The Collaborative International Dictionary of English v.0.48:

Gamble \Gam"ble\, v. i. [imp. & p. p. Gambled; p. pr. & vb. n.
   Gambling.] [Dim. of game. See 2d Game.]
   To play or game for money or other stake.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

gambling \gambling\ n. [p. pr. of gamble.]
   the act of playing for stakes in the hope of winning
   (including the payment of a price for a chance to win a
   prize); as, his gambling cost him a fortune.

   Syn: gaming, play.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

gambling
    n 1: the act of playing for stakes in the hope of winning
         (including the payment of a price for a chance to win a
         prize); "his gambling cost him a fortune"; "there was heavy
         play at the blackjack table" [syn: gambling, gaming,
         play]

Moby Thesaurus II by Grady Ward, 1.0:

35 Moby Thesaurus words for "gambling":
   Cosa Nostra, Mafia, betting, black market, bootlegging,
   cardsharping, casting lots, gaming, gray market, hazarding,
   illegal commerce, illegal operations, illegitimate business,
   illicit business, loan-sharking, moonshining, narcotics traffic,
   organized crime, play, playing, prostitution, protection racket,
   racket, risking, shady dealings, sortition, speculation, sporting,
   staking, the rackets, the syndicate, traffic in women, usury,
   wagering, white slavery