Nouns

(n)speculator, plungersomeone who risks losses for the possibility of considerable gains
(n)diver, plungersomeone who dives (into water)
(n)plunger, plumber's helperhand tool consisting of a stick with a rubber suction cup at one end; used to clean clogged drains
(n)piston, plungermechanical device that has a plunging or thrusting motion