definition of
nullify

[1] #1 nullify v. [invalidate, annul, quash, void, avoid] declare invalid; "The contract was annulled"; "void a plea". wn

[2] #2 nullify v. [invalidate] show to be invalid. wn

[3] #3 nullify v. [neutralize, neutralise, negate] make ineffective by counterbalancing the effect of; "Her optimism neutralizes his gloom"; "This action will negate the effect of my efforts". wn