plunger

(noun) someone who risks losses for the possibility of considerable gains. Synonyms: speculator.

(noun) someone who dives (into water). Synonyms: diver.

(noun) hand tool consisting of a stick with a rubber suction cup at one end; used to clean clogged drains. Synonyms: plumber's helper.

(noun) mechanical device that has a plunging or thrusting motion. Synonyms: piston.