nosedive vs plunge

nosedive and plunge both are nouns.

Word	Noun	Adjective	Verb	Adverb
nosedive	Yes	No	Yes	No
plunge	Yes	No	Yes	No

As verbs, plunge is a hypernym of nosedive; that is, plunge is a word with a broader meaning than nosedive:

Other hypernyms of nosedive include dive, plunk.

nosedive (noun)	plunge (noun)
a steep nose-down descent by an aircraft	a brief swim in water
a sudden sharp drop or rapid decline	a steep and rapid fall

nosedive (verb)	plunge (verb)
plunge nose first; drop with the nose or front first, of aircraft	begin with vigor
	devote (oneself) fully to
	cause to be immersed
	immerse briefly into a liquid so as to wet, coat, or saturate
	thrust or throw into
	fall abruptly
	drop steeply
	dash violently or with great speed or impetuosity