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