The Collaborative International Dictionary of English v.0.48:

Tapster \Tap"ster\, n. [AS. t[ae]ppestre a female tapster. See
   Tap a plug, pipe, and -ster.]
   One whose business is to tap or draw ale or other liquor.
   [1913 Webster]

WordNet (r) 3.0 (2006):

tapster
    n 1: a tavern keeper who taps kegs or casks [syn: tapster,
         tapper]