WILLIAM A. BABLITCH, J.
Plaintiffs in this case are property owners in Racine county who live near a landfill site operated by Land Reclamation, Ltd. (LRL). The plaintiffs' complaint alleges that the landfill was the source of unexpected and unintended pollution causing them bodily injury and property damage. The liability insurance policy issued by Bituminous Casualty Corporation (Bituminous) to LRL excluded pollution damages unless such damages were "sudden and accidental."
The court of appeals agreed with Bituminous that the word "sudden" in the phrase "sudden and accidental" unambiguously means abrupt and immediate and therefore the damages alleged do not come within the coverage of the policy. The property owners argue that their damages are covered by the policy because the word "sudden" is ambiguous and may reasonably mean unexpected and unintended. The phrase is not defined in the policy. Recognized dictionaries differ in the primary meaning of the word. The insurance industry itself has attached different meanings to the word at different times.
We conclude that the word is reasonably susceptible to different meanings and is therefore ambiguous. It is a [742]*742long standing principle of law that any ambiguity in an insurance contract must be construed in favor of the insured, particularly when such ambiguity appears, as it does here, in an exclusionary clause. We therefore hold that unexpected and unintended pollution damages are not excluded from coverage in the insurance policy. The decision of the court of appeals is reversed, and the matter is remanded to the trial court for further proceedings.
The LRL landfill is licensed for operation as a sanitary landfill by the Wisconsin Department of Natural Resources. In 1987, the plaintiffs commenced this action against LRL. Subsequently, Bituminous was pleaded into the action in the plaintiffs' second amended complaint.
Plaintiffs generally allege that over the course of time LRL operated the landfill negligently and in violation of federal, state and local law, rules, ordinances and regulations, resulting in water contamination, noise, dust, smells and blowing garbage. Individual plaintiffs also allege assorted medical problems and a local increase in the pest population. The allegations do not pinpoint any specific dates of discharges within the policy period.
Bituminous issued comprehensive general liability, comprehensive catastrophe liability and commercial umbrella liability policies to LRL from 1971 until September 1,1986. The policies contained the following language in exclusion (f), the pollution exclusion:
This insurance does not apply:
(f) to bodily injury or property damage arising out of the discharge, dispersal, release or escape of smoke, vapors, soot, fumes, acids, alkalis, toxic chemicals, liquids or gases, waste materials or other irritants, contaminants or pollutants into or upon land, the atmosphere or any water course or [743]*743body of water; but this exclusion does not apply if such discharge, dispersal, release or escape is sudden and accidental. . ..
All of the policies issued by Bituminous to LRL afforded coverage for damages caused by an "occurrence." The final set of policies, covering periods from 1980 through 1986, defined "occurrence" as: "an accident, including continuous or repeated exposure to conditions, which results in bodily injury or property damage neither expected nor intended from the standpoint of the insured[.]"1
The policies also included a duty to defend clause. In July 1987, Bituminous originally undertook to defend LRL, but it withdrew in January, 1988, denying coverage for the allegations in the lawsuit citing the applicable policy provisions, and, in particular, exclusion (f), the policy's pollution exclusion. Bituminous then filed a motion for summary judgment in July, 1988, on grounds that the applicable policy provisions did not provide coverage for LRL for the facts as alleged in the plaintiffs' complaint and the facts of the case.
The trial court granted Bituminous' motion for summary judgment. In its memorandum decision dated August 3, 1988, the trial court cited three Wisconsin cases as controlling, Clark v. London & Lancashire Indemnity Co., 21 Wis. 2d 268, 124 N.W.2d 29 (1963); City of Milwaukee v. Allied Smelting Corp., 117 Wis. 2d 377, 344 N.W.2d 523 (Ct. App. 1983); and State v. Mauthe, 142 Wis. 2d 620, 419 N.W.2d 279 (Ct. App. [744]*7441987). Based on these cases, the trial court found that the term "sudden and accidental" did not apply to pollution damage occurring over a substantial period of time. The trial court then determined, based on this construction, that the record in this case did not contain any allegations of any events which raised genuine issues of material fact that could result in coverage. LRL appealed, and the plaintiffs joined LRL as intervenors on the appeal.
The court of appeals affirmed the trial court's grant of summary judgment concluding that the phrase "sudden and accidental" unambiguously means accidental and immediate. LRL petitioned this court for review pursuant to sec. 808.10, Stats., and we granted the petition.
The dispositive issue in this case is one of contract interpretation. The insurance policy itself does not define the meaning of the terms "sudden and accidental." The interpretation of words or clauses in an insurance contract is a question of law which this court decides independently of the decisions of the lower courts. Garriguenc v. Love, 67 Wis. 2d 130, 133, 226 N.W.2d 414 (1975).
In interpreting the definition of the phrase "sudden and accidental," we must first determine whether the language is ambiguous when used in the context of the policy's exclusionary clause.2 Words or phrases in a contract are ambiguous when they are susceptible to more [745]*745than one reasonable interpretation. Katze v. Randolph & Scott Mut. Fire Ins., 116 Wis. 2d 206, 213, 341 N.W.2d 689, 692 (1984). If we determine that the phrase is ambiguous, we must construe the ambiguity in favor of coverage.
Bituminous argues that the phrase "sudden and accidental" unambiguously means abrupt or immediate. We agree that one meaning of the phrase "sudden and accidental" is abrupt or immediate; we disagree that such definition is the only meaning that can reasonably attach to the phrase. When determining the ordinarily understood meaning of a word or phrase, it is appropriate to look to definitions in a recognized dictionary. Lawver v. Boling, 71 Wis. 2d 408, 414, 238 N.W.2d 514 (1976). In doing so, we find that recognized dictionaries differ on the meaning of the term "sudden." Webster's Third New International Dictionary (1986) defines "sudden" in a variety of different ways. Webster's first defines the term as "happening without previous notice . . . occurring unexpectedly . . . not foreseen . . .." Id. at 2284. Only later does Webster's define the word "sudden" in any sense of timeliness, listing the synonyms "prompt" and "immediate." Id. In contrast, the Random House Dictionary of the English Language, (2d ed. 1987), first defines the word "sudden" in temporal terms as "happening, coming, made, or done quickly . . .." Id. at 1900. The very fact that recognized dictionaries differ on the primary definition of "sudden" is evidence in and of itself that the term is ambiguous.
The Georgia Supreme Court recently stated in Claussen v. Aetna Cas. & Sur. Co., 380 S.E.2d 686, 688 (Ga. 1989):
Perhaps, the secondary meaning is so common in the vernacular that it is, indeed, difficult to think [746]*746of 'sudden' without a temporal connotation: a sudden flash, a sudden burst of speed, a sudden bang. But, on reflection one realizes that, even in its popular usage, 'sudden' does not usually describe the duration of an event, but rather its unexpectedness: a sudden storm, a sudden turn in the road, sudden death. Even when used to describe the onset of an event, the word has an elastic temporal connotation that varies with expectations: Suddenly, it's spring. See also Oxford English Dictionary, at 96 (1933) (giving usage examples dating back to 1340, e.g., 'She heard a sudden step behind her'; and, 'A sudden little river crossed my path As unexpected as a serpent comes.')
We conclude that the phrase "sudden and accidental" is susceptible to more than one reasonable meaning, including abrupt and immediate as Bituminous claims as well as unexpected and unintended as the property owners claim. Thus the phrase "sudden and accidental" contained in the pollution exclusion clause is ambiguous.
When ambiguous language appears in an insurance contract, we must construe the ambiguity in favor of the insured and against the insurance company that drafted the ambiguous language. Mercado v. Mitchell, 83 Wis. 2d 17, 25, 264 N.W.2d 532 (1978). This court has consistently stated that this is especially true of exclusionary clauses. E.g., Meiser v. Aetna Casualty & Surety Co., 8 Wis. 2d 233, 238, 98 N.W.2d 919 (1959). Therefore, our conclusion that the phrase is ambiguous requires that we apply the interpretation favoring the insured, and reject the insurers argument that the phrase "sudden and accidental" has only a temporal meaning within the exclusionary clause. We therefore conclude that the phrase "sudden and accidental" means damages that are unexpected and unintended.
[747]*747This conclusion comports with substantial evidence indicating that the insurance industry itself originally intended the phrase to be construed as "unexpected and unintended." This court may examine extrinsic evidence as an aid to determining the meaning of contract language when an insurance contract is ambiguous. See Hope Acres, Inc., v. Harris, 27 Wis. 2d 285, 291, 134 N.W.2d 462 (1965).
Significantly, the insurance policies at issue in this case are standard form comprehensive general liability (CGL) policies that were developed by insurance industry trade associations, which are comprised of almost every major American insurance company.3 Standard form CGL policies have been in use since the 1940s. See Sayler & Zolensky, Pollution Coverage and the Intent of the CGL Drafters: The Effect of Living Backwards, Mealey's Lit. Rpts. (Insurance) 4,425, 4,427 (1987).
Industry-wide revisions of standard CGL provisions occurred in 1966 and again in 1973. Most early CGL policies provided coverage for property damage or personal injury "caused by accident," a term which was not defined in standard form CGL policies. The insurance industry's failure to define this term led to great uncertainty about what constituted an "accident." In Clark, 21 Wis. 2d at 276, this court was called upon to interpret the phrase "caused by accident," and concluded that [748]*748damage from gradual pollution was not covered. However, several other jurisdictions reached the opposite conclusion and found that damages arising from gradual pollution were in fact "caused by accident." In order to clarify the scope of coverage provided by the standard form CGL policy, and respond to policyholder demand for expanded coverage, the insurance industry substantially revised the standard form CGL policy in 1966. Tyler & Wilcox, Pollution Exclusion Clauses: Problems in Interpretation and Application Under the Comprehensive General Liability Policy, 17 Idaho L. Rev. 497, 499 (September 1981).
The standard form policy introduced in 1966 entirely abandoned the phrase "caused by accident." This change was "in response to consumer demands for broader liability protection and in acquiescence to the judicial trend toward a more expansive reading of the term accident . . .." Id. (Footnote omitted.) The new standard occurrence-based policy provided coverage for damage resulting from an "occurrence," which was defined as:
'an accident, including continuous or repeated exposure to conditions, which results in bodily injury or property damage neither expected nor intended from the standpoint of the insured.' Id. (Emphasis added.)
This change in the policy language was widely touted as an important expansion of CGL insurance coverage. Numerous representatives of insurance industry trade associations and the insurance companies that drafted the revised standard form CGL policy actively promoted this policy as providing new, broadened coverage for liabilities arising from gradual pollution. Bradbury at 283. At least with respect to environmental [749]*749claims, contemporaneous industry commentary on the 1966 CGL policy indicates that there was no intent to avoid coverage for unexpected or unintended pollution. G.L. Bean, Assistant Secretary, Liberty Mutual Insurance Company, in a paper presented at the Mutual Insurance Technical Conference, stated: " '[I]t is in the waste disposal area that a manufacturer's basic premises-operation coverage is liberalized most substantially.' " Pendygraft, Plews, Clark & Wright, Who Pays for Environmental Damage: Recent Developments in CERCLA Liability and Insurance Coverage Litigation, 21 Ind. L. Rev. 117, 141 (1988) (Pendygraft).
Lyman J. Baldwin, Jr., Secretary of Underwriting, Insurance Company of North America, amplified this understanding in 1966:
'Let us consider how this would apply in a fairly commonplace situation where we have a chemical manufacturing plant which, during the course of its operations, emits noxious fumes that damage the paint on buildings in the surrounding neighborhood. Under the new policy there is coverage until such time as the insured becomes aware that the damage was being done.' Pendygraft at 142.
The pollution exclusion at issue here was added by a 1973 revision. Under this exclusion, only pollution-related losses that arose from occurrences both "sudden” and "accidental" would be covered. According to various commentators, the exclusion was designed to decrease claims for losses caused by expected or intended pollution by providing an incentive to industry to improve its manufacturing and disposal processes, and unintentional or unexpected damages would still be covered as an "occurrence" under the policy. Broadwell Realty v. Fidelity & Cas., 528 A.2d 76, 84-85 (N.J. Super. Ct. App. Div. 1987); see also Hurwitz and Kohane, The Love [750]*750Canal-Insurance Coverage for Environmental Accidents, 50 Ins. Coun. J. 378-79 (July 1983) (Hurwitz and Kohane).
Contemporaneous representations by the insurance industry confirm that the drafting committee, in creating the exclusionary clause, clarified but did not reduce the scope of coverage. This expressed intent was also the interpretation relied upon by insurance regulators in approving the exclusionary clause when it was submitted for approval to various state insurance commissioners by representatives of the insurance industry.
In May 1970, both insurance industry trade associations, (the Mutual Insurance Rating Bureau and the Insurance Rating Board,) submitted the standard pollution. exclusion for approval by state regulatory authorities throughout the country. U.S. Fid. & Guar. v. Specialty Coatings, 535 N.E.2d 1071, 1077 (Ill. App.), appeal denied, 545 N.E.2d 133 (1989). The Insurance Rating Board offered the following explanation of the exclusion:
'Coverage for pollution or contamination is not provided in most cases under present policies because damages can be said to be expected or intended and thus are excluded by the definition of occurrence. The above exclusion clarifies this situation so as to avoid any question of intent. Coverage is continued for pollution or contamination caused injuries when the pollution or contamination results from an accident . . ..' Price, Evidence Supporting Policyholders in Insurance Coverage Disputes, 3 Nat. Resources & Envir. 17, 48 (Spring 1988). (Emphasis added.)
Some states questioned whether the purpose of the pollution exclusion was "limiting the coverage and not clarifying it." The Mutual Insurance Rating Bureau, which assisted in the draft of the exclusion endorsement, in a submission to the West Virginia Commissioner of [751]*751Insurance, explained that the intent of the clause was to clarify " 'that the definition of occurrence excludes damages that can be said to be expected or intended.' " See Pendygraft at 154. (Emphasis added.) On the basis of this and similar representations, the West Virginia Insurance Commissioner approved the exclusion, stating:
The [insurance] companies and rating organizations have represented to the Insurance Commissioner, orally and in writing, that the proposed exclusions . . . are merely clarifications of existing coverages as defined and limited in the definitions of the term 'occurrence,' contained in the respective policies to which said exclusions would be attached. Price at 48.
Furthermore, documents presented by the Insurance Rating Board to the Georgia Insurance Commissioner when the pollution exclusion clause was first adopted suggest that the clause was intended to exclude only intentional polluters. The Insurance Rating Board represented " 'the impact of the [pollution exclusion clause] on the vast majority of risks would be no change. It is rather a situation of clarification . . . Coverage for expected or intended pollution and contamination is not now present as it is excluded by the definition of occurrence. Coverage for accidental mishaps is continued . . ..' " Claussen v. Aetna Cas. & Sur. Co., 676 F. Supp. 1571, 1573 (S.D. Ga. 1987), question certified, 865 F.2d. 1217 (11th Cir. 1989), certified question answered, 380 S.E.2d. 686, (Ga. 1989), and later op., 888 F.2d 747 (11th Cir. 1989).
An excerpt from The Fire, Casualty & Surety Bulletin, used by insurance agents and brokers to interpret standard insurance policy provisions, also supports this interpretation:
[752]*752'In one important respect, the exclusion simply reinforces the definition of occurrence. That is, the policy states that it will not cover claims where the "damage was expected or intended" by the insured and the exclusion states, in effect, that the policy will cover incidents which are sudden and accidental — unexpected and not intended.' Hurwitz and Kane at 379.
Against this backdrop, a majority of other jurisdictions reaching the issue have interpreted the pollution exclusion clause and the phrase "sudden and accidental," as simply a restatement of the definition of "occurrence." In other words, the policy will cover claims where the injury was "neither expected nor intended." See, e.g., cases cited in Broadwell Realty, 528 A.2d at 83-86; see also cases cited in Claussen v. Aetna Cas. & Sur. Co., 865 F.2d 1217, 1218 (11th Cir. 1989); Rhodes, 12 Couch on Insurance 2d, sec. 44A:122 (Rev. Ed. 1981 & Supp.); Annotation, Construction and Application of Pollution Exclusion Clause in Liability Insurance Policy, 39 ALR4th 1047 (1985).
One of the first such cases arising in New York, Farm Family Mut. Ins. Co. v. Bagley, 64 A.D.2d 1014, 409 N.Y.S.2d 294, 296 (1978), involved a crop spraying operation which caused damage to a neighboring vineyard. The trial court granted the insurer's motion for summary judgment on the grounds of the pollution exclusion, but the New York appellate court reversed, concluding that the language of the exclusion was "not free from ambiguity . .
Three years later, the same court expanded upon this decision in Allstate Ins. Co. v. Klock Oil Co., 73 A.D.2d 486, 426 N.Y.S.2d 603, 605 (1980), which involved damages caused by the defendant's leaking gasoline storage tank:
[753]*753Thus, the negligent installation or maintenance of the storage tank could result in an accidental discharge or escape of gasoline which would be both 'sudden and accidental' though undetected for a substantial period of time (see Employees Insurance Co. of Alabama v. Rives, Ala., 87 So. 2d 653). Also the word 'sudden' as used in liability insurance need not be limited to an instantaneous happening (McGroarty v. Great American Ins. Co., 43 A.D.2d 368, 351 N.Y.S.2d 428, aff'd. 36 N.Y.S.2d 358, 368 N.Y.S.2d 485, 329 N.E.2d 172). The term 'sudden and accidental' must be construed in its relevant context. The relevant context to be considered is the fact that it is a term employed by an insurer in the contract and should be given the construction most favorable to the insured. Id.
The New York Appellate Court affirmed this ruling again in Niagara County v. Utica Mut. Ins. Co., 80 A.D.2d 415, 439 N.Y.S.2d 538 (1981). In explaining the rationale behind the pollution exclusion, which under New York law, is required in all policies issued to commercial or industrial enterprises, the court stated that the exclusion was calculated to buttress New York's strict environmental protection standards, which could be undermined if commercial enterprises were able to purchase insurance to protect themselves from liability arising from their pollution of the environment. After concluding that Niagara County was not an intentional polluter, the court affirmed the lower court's rejection of the insurer's pollution exclusion defense, and ordered it to defend the county in the now celebrated Love Canal litigation.
Other states have also construed the pollution exclusion clause in this fashion. The Washington Court of Appeals addressed the issue in United Pacific Ins. v. Van's Westlake Union, 664 P.2d 1262 (Wash. App.), [754]*754review denied, 100 Wash. 2d 1018 (1983), which again involved a suit brought against the owner of a leaking underground gasoline storage tank. That court held that the trial court had correctly determined that the damages were covered by the policy. The court concluded that the pollution exclusion clause was solely meant to deprive active polluters from coverage, and not to apply where the damage caused was neither expected nor intended. Id. at 1264 (citing Niagara County, 427 N.Y.S.2d at 174). The court went on to explain that to hold otherwise "would permit the ambiguous pollution exclusion clause to unfairly devour much of the policy and relieve the insurer from liability . . .." Van's Westlake, 664 P.2d at 1266. See also Time Oil Co. v. CIGNA Property & Casualty Ins. Co., No. C88-1235R, 4 TXLR 1359 (W.D. Wash. April 2, 1990) (noting that the Van's Westlake decision was consistent with the Washington Supreme Court's decision in Anderson & Middleton Lumber Co. v. Lumberman's Mutual Casualty Co., 333 P.2d 938 (Wash. 1959), which held that the meaning of " 'the word "sudden," ... in common usage, is not "instantaneous" but rather 'unforeseen and unexpected.' '').
In Jackson Tp., Etc. v. Hartford Acc. & Indem., 451 A.2d 990 (N.J. Super. L. 1982), the court summarized the case law on the pollution exclusion clause from other jurisdictions, and concluded in light of the case law that the clause should be interpreted as covering claims where the injury was "neither expected nor intended." The court then proceeded to address the implications of the inclusion of the term "sudden" in the pollution exclusion clause:
The frequency of dumping is not dispositive of the issue of whether the occurrence was sudden or accidental. If the inquiry is, as it should be, whether [755]*755the pleadings charged the insured with an act resulting in unintended or unexpected damage, then the act or acts are sudden and. accidental regardless of how many deposits or dispersals may have occurred, and although the permeation of pollution into the ground water may have been gradual rather than sudden, the behavior of the pollutants as they seeped into the aquifier is irrelevant if the permeation was unexpected. Id. at 994.
The New Jersey Superior Court reaffirmed its Jackson Township decision two years later, in CPS Chem. Co. v. Continental Ins. Co., 489 A.2d 1265, 1270-71 (N.J. Super. L. 1984), reversed on other grounds, 495 A.2d 886 (App. Div. 1985). In that case, CPS Chemical and thirty three others were named as defendants in a suit brought by the city of Philadelphia, arising out of the illegal dumping of toxic wastes, generated by the defendants, in a city dump. The court held that because the hauler's illegal disposed of CPS's wastes were unexpected and unforeseen by CPS, the insurer had to provide coverage under the "sudden and accidental" exception to the pollution exclusion clause. The court explained that it may well have been that the drafters of this clause believed that "sudden and accidental" connoted a sense of dramatic catastrophe immediate in its consequence, but it could not fairly be said that this was unambiguously expressed. Id. See also Summit Assoc. v. Liberty Mut. Fire Ins., 550 A.2d 1235, 1238-39 (N.J. Super. A.D. 1988).
Ohio has also adopted this construction of the pollution exclusion clause. In Buckeye Union Ins. v. Liberty Solv. & Chem., 477 N.E.2d 1227,1234 (Ohio App. 1984), which involved another leaking hazardous waste disposal facility, the court concluded that a "sudden" occurrence is not necessarily an instantaneous one, but merely one [756]*756which has happened without previous notice or on very brief notice. Since there were no allegations that the insured in that case intended or expected the release of hazardous substances, the court held that the pollution exclusion clause did not preclude coverage.
This interpretation was followed in Kipin Industries v. American Univ. Ins., 535 N.E.2d 334, 338 (Ohio App. 1987), which stated:
We interpret the non-applicability clause (emphasized above) in the same way as does the Court of Appeals ... in Buckeye Union, ... an interpretation that is with the weight of authority. In brief, this interpretation is that an event is 'sudden and accidental' and thus not excluded from comprehensive coverage if the damaging result is neither expected nor intended by the insured. Id. (citing Jackson Twp. Municipal Utilities Auth. v. Hartford Acc. & Indemn. Co. [1982], 186 N.J. Super. 156, 162-64, 451 A.2d 990, 993-994). The clause must be construed strictly against the insurer because it is ambiguous in meaning and its subject matter is an exclusion from what is stated to be comprehensive coverage against liability. We find in the record before us a 1970 circular to the members of the Insurance Rating Board that, in discussing exclusion (f), states that the clause is intended to clarify the definition of 'occurrence' so as to exclude coverage for expected or intended results. Id.
Illinois has also cited the above-referenced case law with approval. In Reliance Ins. Co. of Illinois v. Martin, 467 N.E.2d 287, 289 (Ill. App. 1984), the court reversed the trial court's granting of the insurer's summary judgment motion, holding that fumes and soot from the insured's parking garage entered a neighboring condominium "at diverse times and over a period of time" did not mean it was not "sudden and accidental." The court [757]*757stated that the relevant question is not the time frame involved but whether the insured could have intended or expected carbon monoxide and soot to enter the condominium.
More recently, the Illinois Appellate Court reiterated that the wording of the pollution exclusion demonstrates "that any unintentional or unexpected contamination would still be covered as an 'occurrence' under the policy." U.S. Fid. & Guar. v. Specialty Coatings, 535 N.E.2d at 1077.
Michigan courts have also equated the word "sudden" as used in the pollution exclusion clause with the word "unexpected." Jonesville Prod. v. Transamerica Ins. Group, 402 N.W.2d 46 (Mich. App. 1986), leave to appeal denied, 428 Mich. 897 (1987). This holding was reaffirmed in Upjohn Co. v. New Hampshire Ins. Co., 444 N.W.2d 813, 817 (Mich. App. 1989), where the court stated that "even a continuous discharge of chemicals may be both accidental (i.e., unintended) and sudden (i.e., unexpected) and, therefore, outside the pollution exclusion." See also Polkow v. Citizens Ins. Co. of America, 447 N.W.2d 853, 856 (Mich. App. 1989). But see Ray Industries, Inc. v. Liberty Mutual Ins. Co., 728 F. Supp. 1310 (E.D. Mich. 1989); Fl Aerospace v. Aetna Cas. & Sur. Co., 897 F.2d 214 (6th Cir. 1990).
Of course, this is not to say that all courts which have interpreted the pollution exclusion clause have concluded that the phrase "sudden and accidental" is ambiguous. However, the fact that substantial conflicting authority exists with respect to the "correct" interpretation of the exclusionary terms merely serves to strengthen the conclusion that the terms are susceptible to more than one meaning, and thus ambiguous. See Grinnell Mut. Reinsurance Co. v. Wasmuth, 432 N.W.2d 495, 499 (Minn. App. 1988). Although we acknowledge [758]*758that the mere controversy concerning the meaning of a contract term does not itself establish an ambiguity, this type of comprehensive debate dispels the insurers contention that the exclusionary language is clear. See U.S. Fidelity and Guar. Co. v. Thomas Solvent Co., 683 F. Supp. 1139, 1155-56 (W.D. Mich. 1988).
Nevertheless, Bituminous insists that Wisconsin courts have implicitly rejected the line of cases which define "sudden and accidental" to mean "unexpected or unintended." E.g., Allied Smelting, 117 Wis. 2d at 382-386; Mauthe, 142 Wis. 2d at 624-29; Wagner, 145 Wis. 2d at 615-18.
Allied Smelting involved damage caused by the insured's discharge of acid into the sewer system over a period of time, causing deterioration and extensive repairs. Id. at 381. Allied Smelting's insurer moved for summary judgment based on a standard form pollution exclusion clause apparently identical to the clause at issue in the present case.4 In holding the exclusionary clause applicable, the court of appeals reiterated the rationale of our 1963 Clark decision as applied to the phrase "sudden and accidental." The court of appeals stated in Allied Smelting, 117 Wis. 2d at 385-86:
When a condition is caused by accident, our supreme court has limited coverage to: 'injuries caused by a sudden and identifiable event with respect to both location and time. This is intended to rule out exposure injuries, incurred over a period of time, such as the harmful effects of obnoxious fumes, [759]*759stream pollution, vibration or noises.' See Clark v. London & Lancashire Indemnity Co. of America, 21 Wis. 2d 268, 283, 124 N.W.2d 29, 36-37 (1963).
However, Allied Smelting improperly construed the phrase "sudden and accidental" in light of the obsolete accident-based policy existing at the time of Clark rather than the occurrence-based policy introduced in 1966, the pollution exclusion added in 1973, and the changes in circumstances attending those enactments. These errors have been perpetuated by the subsequent court of appeals decisions relying on the Allied Smelting definition of "sudden and accidental." Because of the differences in the involved policies, Allied Smelting, Mauthe, and Wagner are not controlled by Clark, and thus the law set forth in those cases must be overruled.
Finally, Bituminous argues that interpreting the policy language as excluding expected or intended damages will contravene public policy because "businesses, if they believed that in the future the court would rewrite their insurance policy to provide free insurance, would have a reduced incentive to either avoid polluting practices or insure themselves adequately." However, this argument does not square with the ambiguous nature of the policy. As the Michigan Supreme Court has cautioned, " '[t]he courts have no patience with attempts by a paid insurer to escape liability by taking advantage of an ambiguity, a hidden meaning, or a forced construction of the language in a policy, when all question might have been avoided by a more generous or plainer use of words.' " Powers v. Detroit Auto. Inter-Ins. Exchange, 398 N.W.2d 411, 419 (Mich. 1986). We agree that more precise wording, or a definition of "sudden and accidental," if used by the insurers in drafting the policy, would have put the matter beyond reasonable question. The complete elimination of any exception to the exclusion, [760]*760as was done in the policy in effect from September 1, 1985, to September 1, 1986, would have accomplished the same purpose.
Therefore, we conclude that the phrase "sudden and accidental," contained in the pollution exclusion clause, means unexpected and unintended damages. Because the exclusionary clause does not preclude coverage, and the allegations in the complaint together with the depositions, interrogatories and affidavits raise inferences that could support a recovery covered by the policy, the insurance carriers have a duty to defend. Summary judgment should not have been granted. Accordingly, the decision of the court of appeals is reversed and the matter remanded to the trial court for further proceedings.
By the Court — The decision of the court of appeals is reversed and cause remanded to the trial court for further proceedings.