Main entry: negate, neutralise, neutralize, nullify
Definition: make ineffective by counterbalancing the effect of
Usage: Her optimism neutralizes his gloom; This action will negate the effect of my efforts
Main entry: nullify, invalidate
Definition: show to be invalid
Main entry: void, avoid, annul, invalidate, nullify, quash
Definition: declare invalid
Usage: The contract was annulled; void a plea