The Collaborative International Dictionary of English v.0.48:

Pianist \Pi*an"ist\, n. [Cf. F. pianiste, It. pianista.]
   A performer, esp. a skilled performer, on the piano.
   [1913 Webster]

WordNet (r) 3.0 (2006):

pianist
    n 1: a person who plays the piano [syn: pianist, piano
         player]