slug

noun

any of a large number of small, gastropod mollusks, esp. the ones resembling a land snail, but having only a rudimentary internal shell buried in the mantle
a smooth, soft moth (family Eucleidae) or sawfly larva, resembling a slug
a person, vehicle, etc. that moves sluggishly

noun

a small piece or lump of metal; specif., a bullet
☆ a piece of metal shaped like and used in place of a coin in automatic coin machines; esp., such a substitute coin when used illegally
☆ Printing
1. a strip of metal used to add space between lines of type
2. a line of type made in one piece or strip, as by a linotype machine
3. a short heading, often a single word, indicating the subject of copy
Physics a unit of mass, equal to c. 14.6 kg (c. 32.2 lb), to which a force of one pound imparts an acceleration of one foot per second per second

transitive verb slugged, slugging

Printing to insert (a slug) between lines

noun

Slang a single drink, esp. of straight alcoholic liquor

transitive verb slugged, slugging

Informal to hit hard, esp. with the fist or a bat

noun

Informal a hard blow or hit

See slug in American Heritage Dictionary 4