take the plunge

verb (used with object), plunged, plung·ing.

1. 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.
2. 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.
3. Horticulture. to place (a potted plant) up to its rim in soil or in certain other materials, as sand or moss.
4. Surveying. to transit (the telescope of a transit or theodolite).

verb (used without object), plunged, plung·ing.

5. to cast oneself, or fall as if cast, into water, a hole, etc.
6. to rush or dash with headlong haste: to plunge through a crowd.
7. to bet or speculate recklessly: to plunge on the stock market.
8. to throw oneself impetuously or abruptly into some condition, situation, matter, etc.: to plunge into debt.
9. to descend abruptly or precipitously, as a cliff, road, etc.
10. to pitch violently forward, as a horse, ship, etc.

noun

11. act of plunging.
12. a leap or dive, as into water.
13. a headlong or impetuous rush or dash: a plunge into danger.
14. a sudden, violent pitching movement.
15. a place for plunging or diving, as a swimming pool.
16. Geology. pitch1(def 45).

Idioms

17. 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.

verb

1. (usually foll by into) to thrust or throw (something, oneself, etc)they plunged into the sea
2. to throw or be thrown into a certain state or conditionthe room was plunged into darkness
3. (usually foll by into) to involve or become involved deeply (in)he plunged himself into a course of Sanskrit
4. (intr) to move or dash violently or with great speed or impetuosity
5. (intr) to descend very suddenly or steeplythe ship plunged in heavy seas; a plunging neckline
6. (intr) informal to speculate or gamble recklessly, for high stakes, etc

noun

7. a leap or dive as into water
8. informal a swim; dip
9. mainly US a place where one can swim or dive, such as a swimming pool
10. a headlong rusha plunge for the exit
11. a pitching or tossing motion
12. take the plunge informal
    1. to resolve to do something dangerous or irrevocable
    2. to get married

v.late 14c., “to put or thrust violently into,” also intransitive, from Old French plongier “plunge, sink into; plunge into, dive in” (mid-12c., Modern French plonger), from Vulgar Latin *plumbicare “to heave the lead,” from Latin plumbum “lead” (see plumb (n.)). Original notion perhaps is of a sounding lead or a fishing net weighted with lead. Related: Plunged; plunging. Plunging neckline attested from 1949. n.c.1400, “deep pool,” from plunge (v.). From late 15c. as “a sudden pitch forward;” meaning “act of plunging” is from 1711. Figurative use in take the plunge “commit oneself” is from 1845, from earlier noun sense of “point of being in trouble or danger” (1530s). Venture something, commit oneself, as in You’ve been living together for a year, so when are you going to take the plunge and get married? It is also put as make the plunge, plunge alluding to diving in a body of water. [Mid-1800s] see take the plunge.