The Collaborative International Dictionary of English v.0.48:

player piano \player piano\ n.
   A mechanically operated piano that uses a roll of perforated
   paper to activate the keys.

   Syn: mechanical piano, Pianola.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

player piano
    n 1: a mechanically operated piano that uses a roll of
         perforated paper to activate the keys [syn: mechanical
         piano, Pianola, player piano]