plunger

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. One who plunges or dives.
2. n. A device consisting of a rubber suction cup attached to the end of a stick, used to unclog drains and pipes. Also called plumber's helper.
3. n. A machine part, such as a piston, that operates with a thrusting or plunging movement.

Century Dictionary and Cyclopedia

1. n. One who or that which plunges.
2. n. A cavalryman; in the plural, cavalry.
3. n. A reckless better; a dashing or venturesome gambler or speculator.
4. n. A part of a machine or piece of mechanism that plunges. , , , The piston of a Cornish pump. It is a cylindrical mass of iron which plays through a stuffing-box up and down in the plunger-case, and forces the water into the lift or tube, in which it rises to the surface, adit-level, or other desired point
5. n. In pottery, a vessel in which clay is beaten by a wheel to the required consistency.

Wiktionary

1. n. A device that is used to remove blockages from a toilet or sink by suction.
2. n. The internal piece of a syringe that pushes out or pulls in any contents.
3. n. The sliding activator of an exploder, an electrical generator used to trigger electrical detonators such as blasting caps.
4. n. The part of a cafetière that is pushed down to remove grounds from coffee.
5. n. One who plunges; a diver.
6. n. A device similar to a piston but without a mechanism; a long solid cylinder used, instead of a piston or bucket, as a forcer in pumps.
7. n. The moving portion of solenoid.
8. n. pinball The spring-loaded assembly that propels the ball onto the table.
9. n. dated, slang A reckless gambler.
10. n. pottery A boiler in which clay is beaten by a wheel to a creamy consistency.
11. n. firearms The firing pin of a breechloader.

GNU Webster's 1913

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

WordNet 3.0

1. n. hand tool consisting of a stick with a rubber suction cup at one end; used to clean clogged drains
2. n. someone who risks losses for the possibility of considerable gains
3. n. mechanical device that has a plunging or thrusting motion
4. n. someone who dives (into water)