nosedive

nose·dive  (nzdv)

n.

1. A very steep dive of an aircraft.

2. A sudden, swift drop or plunge: Stock prices took a nosedive.

Thesaurus

Noun	1.	nosedive - a sudden sharp drop or rapid decline; "the stock took a nosedive" decline, diminution - change toward something smaller or lower
	2.	nosedive - a steep nose-down descent by an aircraft nose dive, dive descent - the act of changing your location in a downward direction power dive - a dive of an airplane that is accelerated both by gravity and by the power of the engine
Verb	1.	nosedive - plunge nose first; drop with the nose or front first, of aircraft air travel, aviation, air - travel via aircraft; "air travel involves too much waiting in airports"; "if you've time to spare go by air" dive, plunge, plunk - drop steeply; "the stock market plunged"