strike down
     v 1: declare null and void; make ineffective; "Cancel the
          election results"; "strike down a law" [syn: {cancel}]
     2: cause to die, especially suddenly; "The disease struck down
        many young men in the village"
     3: cause to fall by or as if by delivering a blow; "strike down
        a tree"; "Lightning struck down the hikers" [syn: {fell},
        {drop}, {cut down}]
Source: WordNet® 2.0