From WordNet (r) 3.0 (2006):
plug
n 1: blockage consisting of an object designed to fill a hole
tightly [syn: plug, stopper, stopple]
2: a wad of something chewable as tobacco [syn: chew, chaw,
cud, quid, plug, wad]
3: blatant or sensational promotion [syn: ballyhoo, hoopla,
hype, plug]
4: electrical device that fits into the cylinder head of an
internal-combustion engine and ignites the gas by means of an
electric spark [syn: spark plug, sparking plug, plug]
5: an electrical device with two or three pins that is inserted
in a socket to make an electrical connection [syn: plug,
male plug]
6: an upright hydrant for drawing water to use in fighting a
fire [syn: fireplug, fire hydrant, plug]
7: an old or over-worked horse [syn: hack, jade, nag,
plug]
v 1: fill or close tightly with or as if with a plug; "plug the
hole"; "stop up the leak" [syn: plug, stop up,
secure]
2: persist in working hard; "Students must plug away at this
problem" [syn: plug, plug away]
3: deliver a quick blow to; "he punched me in the stomach" [syn:
punch, plug]
4: make a plug for; praise the qualities or in order to sell or
promote
5: insert a plug into; "plug the wall"
6: insert as a plug; "She plugged a cork in the wine bottle"