The Collaborative International Dictionary of English v.0.48:

Bandit \Ban"dit\ (b[a^]n"d[i^]t), n.; pl. Bandits
   (b[a^]n"d[i^]ts), or Banditti (b[a^]n*d[i^]t"t[i^]). [It.
   bandito outlaw, p. p. of bandire to proclaim, to banish, to
   proscribe, LL. bandire, bannire. See Ban an edict, and cf.
   Banish.]
   An outlaw; a brigand.
   [1913 Webster]

         No savage fierce, bandit, or mountaineer. --Milton.
   [1913 Webster]

   Note: The plural banditti was formerly used as a collective
         noun.
         [1913 Webster]

               Deerstealers are ever a desperate banditti. --Sir
                                                  W. Scott.
         [1913 Webster]

WordNet (r) 3.0 (2006):

bandit
    n 1: an armed thief who is (usually) a member of a band [syn:
         bandit, brigand]