WordNet (r) 3.0 (2006):

Benedict Arnold
    n 1: United States general and traitor in the American
         Revolution; in 1780 his plan to surrender West Point to the
         British was foiled (1741-1801) [syn: Arnold, Benedict
         Arnold]

Moby Thesaurus II by Grady Ward, 1.0:

28 Moby Thesaurus words for "Benedict Arnold":
   Brutus, Judas, Judas Iscariot, Quisling, archtraitor, betrayer,
   cockatrice, conniver, conspirator, conspirer, double agent,
   double-crosser, double-dealer, informer, intrigant, intriguer,
   machinator, plotter, quisling, rat, schemer, serpent, snake,
   timeserver, traitor, treasonist, trimmer, turncoat