The Collaborative International Dictionary of English v.0.48:

Tippler \Tip"pler\, n.
   1. One who keeps a tippling-house. [Obs.] --Latimer.
      [1913 Webster]

   2. One who habitually indulges in the excessive use of
      spirituous liquors, whether he becomes intoxicated or not.
      [1913 Webster]

WordNet (r) 3.0 (2006):

tippler
    n 1: someone who drinks liquor repeatedly in small quantities
         [syn: tippler, social drinker]