quash in WordNet English dictionary

1. declare invalid
   "The contract was annulled"; "void a plea"
   invalidate  annul  quash  void  avoid  nullify 
   
2. put down by force or intimidation
   "The government quashes any attempt of an uprising"; "China keeps down her dissidents very efficiently"; "The rich landowners subjugated the peasants working the land"
   repress  quash  keep down  subdue  subjugate  reduce