Plun″ger (?), n. 1. One who, or that which, plunges; a diver.
2. A long solid cylinder, used, instead of a piston or bucket, as a forcer in pumps.
3. One who bets heavily and recklessly on a race; a reckless speculator.
4. (Pottery) A boiler in which clay is beaten by a wheel to a creamy consistence. Knight.
5. (Gun.) The firing pin of a breechloader.
Plunger bucket, a piston, without a valve, in a pump. — Plunger pole, the pump rod of a pumping engine. — Plunger pump, a pump, as for water, having a plunger, instead of a piston, to act upon the water. It may be single-acting or double-acting