frustrate
     v 1: hinder or prevent (the efforts, plans, or desires) of; "What
          ultimately frustrated every challenger was Ruth's
          amazing September surge"; "foil your opponent" [syn: {thwart},
           {queer}, {spoil}, {scotch}, {foil}, {cross}, {baffle},
          {bilk}]
     2: treat cruelly; "The children tormented the stuttering
        teacher" [syn: {torment}, {rag}, {bedevil}, {crucify}, {dun}]
Source: WordNet® 2.0