The Collaborative International Dictionary of English v.0.48:

Bartender \Bar"tend`er\, n.
   A barkeeper.
   [1913 Webster]

WordNet (r) 3.0 (2006):

bartender
    n 1: an employee who mixes and serves alcoholic drinks at a bar
         [syn: bartender, barman, barkeep, barkeeper,
         mixologist]