material fact

Short definition from Wiktionary

Noun

1. 1
   A fact essential to make a case or a defense, or the absence of which negates a case or defense.
2. 2
   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.
3. 3
   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.