The Collaborative International Dictionary of English v.0.48:

Billiards \Bil"liards\, n. [F. billiard billiards, OF. billart
   staff, cue form playing, fr. bille log. See Billet a
   stick.]
   A game played with ivory balls o a cloth-covered, rectangular
   table, bounded by elastic cushions. The player seeks to impel
   his ball with his cue so that it shall either strike (carom
   upon) two other balls, or drive another ball into one of the
   pockets with which the table sometimes is furnished.
   [1913 Webster]

WordNet (r) 3.0 (2006):

billiards
    n 1: any of several games played on rectangular cloth-covered
         table (with cushioned edges) in which long tapering cue
         sticks are used to propel ivory (or composition) balls