Plunger

1. n. The firing pin of a breechloader.
2. n. One who, or that which, plunges; a diver.
3. n. A long solid cylinder, used, instead of a piston or bucket, as a forcer in pumps.
4. n. One who bets heavily and recklessly on a race; a reckless speculator.
5. n. A boiler in which clay is beaten by a wheel to a creamy consistence.

The word meanings were obtained from OPTED(The Online Plain Text English Dictionary), which is based on “The Project Gutenberg Etext of Webster’s Unabridged Dictionary” which is in turn based on the 1913 US Webster’s Unabridged Dictionary (See Project Gutenburg), as a text file.