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:

Gamble \Gamble\, v. t.
   To lose or squander by gaming; -- usually with away.
   "Bankrupts or sots who have gambled or slept away their
   estates." --Ames.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Gamble \Gam"ble\, n.
   An act of gambling; a transaction or proceeding involving
   gambling; hence, anything involving similar risk or
   uncertainty. [Colloq.]
   [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

gamble
    n 1: money that is risked for possible monetary gain
    2: a risky act or venture
    v 1: take a risk in the hope of a favorable outcome; "When you
         buy these stocks you are gambling" [syn: gamble,
         chance, risk, hazard, take chances, adventure,
         run a risk, take a chance]
    2: play games for money

Moby Thesaurus II by Grady Ward, 1.0:

138 Moby Thesaurus words for "gamble":
   accidentality, actuarial calculation, admit of, adventitiousness,
   ante, ante up, back, be liable, be subjected to, bet, bet on,
   bid fair to, blind bargain, borderline case, brave, break, call,
   cast lots, casualness, challenge, chance, compromise, contingency,
   count on, court destruction, cover, cut lots, cut the cards, dare,
   defy, defy danger, destiny, double contingency, draw lots,
   draw straws, encounter danger, endanger, expose, face, face up to,
   fade, fate, flukiness, forget the odds, fortuitousness, fortuity,
   fortune, gamble on, gamble with, game, good fortune, good luck,
   guess, hap, happenstance, happy chance, hazard, heedless hap,
   how they fall, imperil, incur danger, indeterminacy,
   indeterminateness, jeopard, jeopardize, jeopardy, law of averages,
   lay, lay a wager, lay down, lay open, lie under, lot, luck,
   make a bet, make book, match coins, meet a bet, moira,
   open question, opportunity, parlay, pass, peril,
   piece of guesswork, play, play against, play at dice,
   play the ponies, play with fire, plunge, predict,
   principle of indeterminacy, probability, problematicness,
   prognosticate, punt, put in danger, put in jeopardy, put on,
   question, raffle off, random sample, rely on, risk, run of luck,
   run the chance, run the risk, see, serendipity, set, shoot craps,
   sight-unseen transaction, speculate, speculation, sport, stake,
   stand a chance, stand fair to, stand pat, stand to gain,
   stand to lose, statistical probability, take a chance,
   take chances, tempt Providence, tempt fortune, the breaks,
   theory of probability, toss, toss-up, touch and go, uncertainty,
   uncertainty principle, undecided issue, venture, wager,
   whatever comes