slug

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Any of various terrestrial gastropod mollusks having a slow-moving slimy elongated body with no shell or with a flat rudimentary shell on or under the skin, usually found in moist habitats.
• noun A sea slug.
• noun The smooth soft larva of certain insects, such as the sawfly.
• noun A slimy mass of aggregated amoeboid cells that develops into the spore-bearing fruiting body of a cellular slime mold.
• noun Informal A sluggard.
• noun A round bullet larger than buckshot.
• noun A shot of liquor.
• noun An amount of liquid, especially liquor, that is swallowed in one gulp; a swig.
• noun A small metal disk for use in a vending or gambling machine, especially one used illegally.
• noun A lump of metal or glass prepared for further processing.
• noun A strip of type metal, less than type-high and thicker than a lead, used for spacing.
• noun A line of cast type in a single strip of metal.
• noun A compositor's type line of identifying marks or instructions, inserted temporarily in copy.
• noun Physics The British unit of mass that accelerates at the rate of one foot per second per second when acted on by a force of one pound on the surface of the Earth.
• transitive verb Printing To add slugs to.
• transitive verb Informal To drink rapidly or in large gulps.
• intransitive verb To wait for or obtain a ride to work by standing at a roadside hoping to be picked up by a driver who needs another passenger to use the HOV lanes of a highway.
• noun A commuter who slugs.
• transitive verb To strike heavily, especially with the fist or a bat.
• noun A hard heavy blow, as with the fist or a baseball bat.

from The Century Dictionary.

• noun A terrestrial pulmonate gastropod of one of the families Limacidæ and Arionidæ and related ones, which has only a rudimentary shell, if any.
• noun Some or any slug-like soft-bodied insect or its larva; a grub: as, the yellow-spotted willow-slug, the larva of a saw-fly, Nematus ventralis. See pear-slug, rose-slug, slug-caterpillar, slug-worm.
• noun The trepang or sea-cucumber; any edible holothurian; a sea-slug.
• noun A rather heavy piece of crude metal, frequently rounded in form.
• noun Specifically— A bullet not regularly formed and truly spherical, such as were frequently used with smooth-bore guns or old-fashioned rifies. These were sometimes hammered, sometimes chewed into an approximately spherical form.
• noun Hence— Any projectile of irregular shape, as one of the pieces constituting mitraille
• noun A thick blank of typemetal made to separate lines of print and to show a line of white space; also, such a piece with a number or word, to be used temporarily as a direction or marking for any purpose, as in newspaper composing-rooms the distinctive number placed at the beginning of a compositor's “take,” to mark it as his work. Thin blanks are known as leads. All blanks thicker than one sixteenth of an inch are known as slugs, and are called by the names of their proper typebodies: as, nonpareil slugs; pica slugs
• noun A stunted horn. Compare scur.
• noun A lead of extra thickness used to widen the space between lines of type.
• noun In mech., a name proposed by Worthington for the mass to which a gravitational unit of force must be applied to produce a foot-pound unit of acceleration; 32.2 (or g) times the mass of a standard pound.
• noun In mining, a loop made in a rope for convenience in descending a shallow shaft, the miner putting his leg through the loop, by which he is supported while being lowered by the man at the windlass.
• To be slow, dull, or inert; be lazy; lie abed: said of persons or of things.
• To make sluggish.
• To hinder; retard.
• To strike heavily. Compare slugger.
• noun A heavy or forcible blow; a hard hit.
• To load with a slug or slugs, as a gun.
• In gunnery, to assume the sectional shape of the bore when fired: said of a bullet slightly larger than the bore.
• Slow; sluggish.
• noun A slow, heavy, lazy fellow; a sluggard; a slow-moving animal.
• noun Hence Any slow-moving thing.
• noun A hindrance; an obstruction.

from the GNU version of the Collaborative International Dictionary of English.

• intransitive verb obsolete To move slowly; to lie idle.
• intransitive verb To become reduced in diameter, or changed in shape, by passing from a larger to a smaller part of the bore of the barrel; -- said of a bullet when fired from a gun, pistol, or other firearm.
• noun A drone; a slow, lazy fellow; a sluggard.
• noun obsolete A hindrance; an obstruction.
• noun (Zoöl.) Any one of numerous species of terrestrial pulmonate mollusks belonging to Limax and several related genera, in which the shell is either small and concealed in the mantle, or altogether wanting. They are closely allied to the land snails.