Source : Webster's Revised Unabridged Dictionary (1913)

Dipsomaniac \Dip`so*ma"ni*ac\, n.
   One who has an irrepressible desire for alcoholic drinks.

Source : WordNet®

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