vitiate in WordNet English dictionary

1. corrupt morally or by intemperance or sensuality
   "debauch the young people with wine and women"; "Socrates was accused of corrupting young men"; "Do school counselors subvert young children?"; "corrupt the morals"
   corrupt  pervert  subvert  demoralize  demoralise  debauch  debase  profane  vitiate  deprave  misdirect 
   
2. make imperfect
   "nothing marred her beauty"
   mar  impair  spoil  deflower  vitiate 
   
3. take away the legal force of or render ineffective
   "invalidate a contract"
   invalidate  void  vitiate