Merriam-Webster's Collegiate® Dictionary, 11th Edition
GAMBLE
I. verb (gambled; gambling)
Etymology: probably back-formation from gambler, probably alteration of obsolete gamner, from obsolete gamen to play
Date: 1772
intransitive verb
1. to play a game for money or property, to bet on an uncertain outcome, to stake something on a contingency ; take a chance, transitive verb to risk by gambling ; wager , venture , hazard , gambler noun
II. noun
Date: 1823
1. an act having an element of risk, something chancy, the playing of a game of chance for stakes