Pronunciation: (vish'ē-āt"), [key]
—v.t., -at•ed, -at•ing.
1. to impair the quality of; make faulty; spoil.
2. to impair or weaken the effectiveness of.
3. to debase; corrupt; pervert.
4. to make legally defective or invalid; invalidate: to vitiate a claim.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.