good deal vs inundation

good deal and inundation both are nouns.

Word	Noun	Adjective	Verb	Adverb
good deal	Yes	No	No	No
inundation	Yes	No	No	No

As nouns, inundation is a hyponym of good deal; that is, inundation is a word with a more specific, narrower meaning than good deal:

Other hyponyms of good deal include deluge, flood, torrent, haymow.

good deal (noun)	inundation (noun)
(often followed by `of') a large number or amount or extent	the rising of a body of water and its overflowing onto normally dry land
	an overwhelming number or amount