Vitiate
Defined in 2 dictionaries — Black's (1910), Anderson (1889)
Black's Law Dictionary
Henry Campbell Black, M.A. · 1910
To impair; to make void or voidable; to cause to fail of force or effect; to destroy or annul, either entirely or in part, the legal efficacy and binding force of an act or instrument; as when it is said that fraud vitiates a contract.
A Dictionary of Law
William C. Anderson · 1889