Noun
(law) A fact essential to make a case or a defense, or the absence of which negates a case or defense.
(law, property law) A fact that might alter a person's decision to buy a property or change the terms and price a buyer is willing to accept.
(law, insurance law) A fact that might alter an insurer's decision to agree to provide insurance to a person or alter the terms and conditions or the rate of premium on a policy.
Source: en.wiktionary.org