The Collaborative International Dictionary of English v.0.48:

game room \game" room`\ (g[=a]m"r[=oo]m`), n.
   a recreation room for noisy activities (parties or children's
   play etc) or for table games.

   Syn: rumpus room, playroom, game room. [WordNet 1.5]

WordNet (r) 3.0 (2006):

game room
    n 1: a recreation room for noisy activities (parties or
         children's play etc) [syn: rumpus room, playroom, game
         room]