The Collaborative International Dictionary of English v.0.48:

Gambler \Gam"bler\, n.
   One who gambles.
   [1913 Webster]

WordNet (r) 3.0 (2006):

gambler
    n 1: a person who wagers money on the outcome of games or
         sporting events
    2: someone who risks loss or injury in the hope of gain or
       excitement [syn: gambler, risk taker]