The Collaborative International Dictionary of English v.0.48:

Entertainer \En`ter*tain"er\, n.
   1. One who entertains; a host.
      [1913 Webster]

   2. one who amuses people, such as a singer, dancer, comedian,
      magician, etc., especially one who does so as a
      profession.
      [PJC]

WordNet (r) 3.0 (2006):

entertainer
    n 1: a person who tries to please or amuse