annul


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

     v 1: declare invalid; "The contract was annulled"; "avoid a plea"
          [syn: invalidate, quash, void, avoid, nullify]
          [ant: validate]
     2: annul by recalling or rescinding; "He revoked the ban on
        smoking"; "lift an embargo"; "vacate a death sentence"
        [syn: revoke, lift, countermand, reverse, repeal,
         overturn, rescind, vacate]