quash
verb [ T ]
uk/kwɒʃ/ us LAW
to state officially that something, especially an earlier official decision, is no longer to be accepted:
quash a conviction/decision/order His conviction was quashed in March after a lengthy legal battle.
to forcefully stop something that you do not want to happen:
The company moved quickly to quash rumours of trading losses.
The engineering group yesterday quashed speculation that it was a takeover target.