saboteur

from WordNet (r) 3.0 (2006)
saboteur
    n 1: someone who commits sabotage or deliberately causes wrecks
         [syn: {saboteur}, {wrecker}, {diversionist}]
    2: a member of a clandestine subversive organization who tries
       to help a potential invader [syn: {fifth columnist},
       {saboteur}]
    

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