to cast or thrust forcibly or suddenly into something, as a liquid, a penetrable substance, a place, etc.; immerse; submerge: to plunge a dagger into one's heart.
to bring suddenly or forcibly into some condition, situation, etc.: to plunge a country into war; to pull a switch and plunge a house into darkness.
Horticulture. to place (a potted plant) up to its rim in soil or in certain other materials, as sand or moss.
Surveying. to transit (the telescope of a transit or theodolite).
verb (used without object),plunged,plung·ing.
to cast oneself, or fall as if cast, into water, a hole, etc.
to rush or dash with headlong haste: to plunge through a crowd.
to bet or speculate recklessly: to plunge on the stock market.
to throw oneself impetuously or abruptly into some condition, situation, matter, etc.: to plunge into debt.
to descend abruptly or precipitously, as a cliff, road, etc.
to pitch violently forward, as a horse, ship, etc.
noun
act of plunging.
a leap or dive, as into water.
a headlong or impetuous rush or dash: a plunge into danger.
a sudden, violent pitching movement.
a place for plunging or diving, as a swimming pool.
Geology. pitch1 (def. 45).
Idioms for plunge
take the plunge, to enter with sudden decision upon an unfamiliar course of action, as after hesitation or deliberation: She took the plunge and invested her entire savings in the plan.
Origin of plunge
1325–75; Middle English <Middle French plung(i)er ≪ Vulgar Latin *plumbicāre to heave the lead. See plumb