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]

Moby Thesaurus II by Grady Ward, 1.0:

26 Moby Thesaurus words for "bartender":
   barkeep, barkeeper, barmaid, barman, bootlegger, brewer,
   brewmaster, busboy, carhop, counterman, distiller, headwaiter,
   hostess, liquor dealer, liquor store owner, mixologist, moonshiner,
   publican, sommelier, tapster, tapstress, vintner, waiter, waitress,
   wine merchant, wine steward