The Collaborative International Dictionary of English v.0.48:

Monte \Mon"te\ (m[o^]n"t[asl]), n. [Sp., lit., mountain, hence,
   the stock of cards remaining after laying out a certain
   number, fr. L. mons, montis, mountain.]
   A favorite gambling game among Spaniards, played with dice or
   cards.
   [1913 Webster]

   three-card monte a gambling game using playing cards, in
      which a dealer shows a bettor three cards face up and
      specifies one to be identified, and after the cards are
      turned face down and moved around quickly, the bettor must
      identify which of the three cards is the specified card.
      It is sometimes engaged in by dealers on the streets of a
      city, with bets made by passers-by.
      [PJC]

WordNet (r) 3.0 (2006):

three-card monte
    n 1: a gambling card game of Spanish origin; 3 or 4 cards are
         dealt face up and players bet that one of them will be
         matched before the others as the cards are dealt from the
         pack one at a time [syn: monte, four-card monte,
         three-card monte]