Source : Webster's Revised Unabridged Dictionary (1913)

Vitiation \Vi`ti*a"tion\, n. [L. vitiatio.]
   The act of vitiating, or the state of being vitiated;
   depravation; corruption; invalidation; as, the vitiation of
   the blood; the vitiation of a contract.

         The vitiation that breeds evil acts.     --G. Eliot.

Source : WordNet®

vitiation
     n : nullification by the destruction of the legal force;
         rendering null; "the vitiation of the contract"