A Slug

Any of many terrestrial pulmonate gastropod mollusks, having no (or only a rudimentary) shell. [from early 18^th c.]
(obsolete) A slow, lazy person; a sluggard. [from early 15^th c.]
A bullet (projectile). [from 1620s] Slug (projectile) - Wikipedia
A counterfeit coin, especially one used to steal from vending machines. [from 1880s] Slug (coin) - Wikipedia
A shot of a drink, usually alcoholic. [from 1750s]
(journalism) A title, name or header, a catchline, a short phrase or title to indicate the content of a newspaper or magazine story for editing use. [from 1920s]
(physics, rarely used) the Imperial (English) unit of mass that accelerates by 1 foot per second squared (1 ft/s²) when a force of one pound-force (lbf) is exerted on it. Slug (unit) - Wikipedia
A discrete mass of a material that moves as a unit, usually through another material.
A motile pseudoplasmodium formed by amoebae working together.
(television editing) A black screen.
(letterpress typography) A piece of type metal imprinted by a linotype machine; also a black mark placed in the margin to indicate an error; also said in application to typewriters; type slug.
(regional) A stranger picked up as a passenger to enable legal use of high occupancy vehicle lanes.
(US, slang, District of Columbia) A hitchhiking commuter.
(web design) The last part of a clean URL, the displayed resource name, similar to a filename.
(obsolete) A hindrance, an obstruction.
A ship that sails slowly.