descent vs crash dive

descent and crash dive both are nouns.

Word	Noun	Adjective	Verb	Adverb
descent	Yes	No	No	No
crash dive	Yes	No	No	No

As nouns, crash dive is a hyponym of descent; that is, crash dive is a word with a more specific, narrower meaning than descent:

Other hyponyms of descent include jump, parachuting, dive, nose dive, nosedive, abseil, rappel, swoop, drop, collapse, flop.

descent (noun)	crash dive (noun)
the act of changing your location in a downward direction	a rapid descent by a submarine
properties attributable to your ancestry
a movement downward
the hereditary derivation of an individual
a downward slope or bend
the kinship relation between an individual and the individual's progenitors