Source : Webster's Revised Unabridged Dictionary (1913)

Slugger \Slug"ger\, n.
   One who strikes heavy blows; hence, a boxer; a prize fighter.
   [Cant or Slang]

Source : WordNet®

slugger
     n 1: (baseball) a ballplayer who is batting [syn: {batter}, {hitter},
           {batsman}]
     2: a boxer noted for an ability to deliver hard punches [syn: {slogger}]