Source : Webster's Revised Unabridged Dictionary (1913)

Slug \Slug\, v. t. [imp. & p. p. {Slugged}; p. pr. & vb. n.
   {Slugging}.]
   1. To load with a slug or slugs; as, to slug a gun.

   2. To strike heavily. [Cant or Slang]

Source : WordNet®

slug
     n 1: a projectile that is fired from a gun [syn: {bullet}]
     2: an idle slothful person [syn: {sluggard}]
     3: any of various terrestrial gastropods having an elongated
        slimy body and no external shell
     v 1: strike heavily, especially with the fist or a bat; "He
          slugged me so hard that I passed out" [syn: {slog}, {swig}]
     2: be idle; exist in a changeless situation; "The old man sat
        and stagnated on his porch"; "He slugged in bed all
        morning" [syn: {idle}, {laze}, {stagnate}] [ant: {work}]
     [also: {slugging}, {slugged}]

slugging
     See {slug}