The Collaborative International Dictionary of English v.0.48:

Boozer \Booz"er\, n.
   One who boozes; a toper; a guzzler of alcoholic liquors; a
   bouser.
   [1913 Webster]

WordNet (r) 3.0 (2006):

boozer
    n 1: a person who drinks alcohol to excess habitually [syn:
         alcoholic, alky, dipsomaniac, boozer, lush,
         soaker, souse]