WordWeb Online

1. Corrupt morally or by intemperance or sensuality
   - corrupt, pervert, subvert, demoralize, demoralise [Brit], debauch, debase, profane, deprave, misdirect
    
2. Make imperfect
   - mar, impair, spoil, deflower
    
3. Take away the legal force of or render ineffective
   - invalidate, void

Derived forms: vitiates, vitiated, vitiating

See also: vitiation

Type of: alter, change, damage, modify