The verb quash has 2 senses (first 1 from tagged texts)
1. (1) repress, quash, keep down, subdue, subjugate, reduce -- (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")
2. invalidate, annul, quash, void, avoid, nullify -- (declare invalid; "The contract was annulled"; "void a plea")