nullify


nullify (http://definr.com/nullify)

     v 1: declare invalid; "The contract was annulled"; "avoid a plea"
          [syn: invalidate, annul, quash, void, avoid]
          [ant: validate]
     2: show to be invalid [syn: invalidate] [ant: validate]
     3: make ineffective by counterbalancing the effect of; "Her
        optimism neutralizes his gloom" [syn: neutralize, neutralise]