[plunge] vb plunged ; plung.ing [ME, fr. MF plonger, fr. (assumed) VL plumbicare, fr. L plumbum lead] vt (14c) 1: to cause to penetrate or enter quickly and forcibly into something
2: to cause to enter a state or course of action usu. suddenly, unexpectedly, or violently ~ vi 1: to thrust or cast oneself into or as if into water
2. a: to become pitched or thrown headlong or violently forward and downward; also: to move oneself in such a manner b: to act with reckless haste: enter suddenly or unexpectedly c: to bet or gamble heavily and recklessly
3: to descend or dip suddenly
[2]plunge n (15c): an act or instance of plunging: dive; also: swim