1. A drone; a slow, lazy fellow; a sluggard.
2. A hindrance; an obstruction.
3. (Science: zoology) 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.
4. (Science: zoology) Any smooth, soft larva of a sawfly or moth which creeps like a mollusk; as, the pear slug; rose slug.
5. A ship that sails slowly. His rendezvous for his fleet, and for all slugs to come to, should be between Calais and Dover. (Pepys)
6. [Perhaps a different word] An irregularly shaped piece of metal, used as a missile for a gun.
7. A thick strip of metal less than type high, and as long as the width of a column or a page, used in spacing out pages and to separate display lines, etc. Sea slug.
8. (Science: zoology) Any nudibranch mollusk. A holothurian. Slug caterpillar. Same as slugworm.
Origin: OE. Slugge slothful, sluggen to be slothful; cf. LG. Slukk low-spirited, sad, E. Slack, slouch, D. Slak, slek, a snail.