Vitiate
VI'TIATE, verb transitive [Latin vitio. See vice and Viciate.]
1. To injure the substance or qualities of a thing, so as to impair or spoil its use and value. Thus we say, luxury vitiates the humors of the body; evil examples vitiate the morals of youth; language is vitiated by foreign idioms.
This undistinguishing complaisance will vitiate the taste of readers.
2. To render defective; to destroy; as the validity or binding force of an instrument or transaction. Any undue influence exerted on a jury vitiates their verdict. Fraud vitiates a contract.