deluge vs flash flood

deluge and flash flood both are nouns.

Word	Noun	Adjective	Verb	Adverb
deluge	Yes	No	Yes	No
flash flood	Yes	No	No	No

As nouns, flash flood is a hyponym of deluge; that is, flash flood is a word with a more specific, narrower meaning than deluge:

deluge: the rising of a body of water and its overflowing onto normally dry land
flash flood: a sudden local flood of great volume and short duration

Other hyponyms of deluge include debacle, flashflood, Noachian deluge, Noah's flood, Noah and the Flood, the Flood.

deluge (noun)	flash flood (noun)
a heavy rain	a sudden local flood of great volume and short duration
the rising of a body of water and its overflowing onto normally dry land
an overwhelming number or amount

deluge (verb)	flash flood (verb)
fill or cover completely, usually with water
charge someone with too many tasks
fill quickly beyond capacity; as with a liquid