Definition of: plug

(plug) noun
1. Anything, as a piece of wood or a cork, used to stop a hole; a wedge or peg driven into anything.
2. A spark plug.
3. Electr. A device containing conducting material, as projecting prongs, for inserting in an outlet, etc., so as to complete a circuit or make contact.
4. A flat cake of pressed or twisted tobacco.
5. Any worn–out or useless thing, particularly a horse past its prime: often with old.
6. U.S. Slang A man's high silk hat; also plug hat.
7. Slang Mention of a product, song, etc., as on a radio or television program, to give it publicity; an advertisement.
8. Geol. The hard core of igneous rock which fills the neck of a volcano.
9. The discharge outlet from a water main: also called hydrant.
10. Mech. The cylindrical part of a cylinder lock which contains the keyhole and is turned by the key.
11. In angling, a type of lure, usually cylindrical and with several hooks attached, similar to a spoon.
—v. plugged, plug·ging v.i.
1. To stop or close, as a hole, by inserting a plug: often with up.
2. To insert as a plug.
3. Slang To shoot a bullet into.
4. U.S. Slang To advertise frequently or insistently; publicize.
—v.i.
5. Colloq. To work doggedly; persevere.
—to plug in To insert the plug of (a lamp, etc.) in an electrical outlet. [<MDu. plugge]
—plug′ger noun