flood vs inundate

flood is a noun but inundate is not a noun.

Word	Noun	Adjective	Verb	Adverb
flood	Yes	No	Yes	No
inundate	No	No	Yes	No

As verbs, inundate is a hyponym of flood; that is, inundate is a word with a more specific, narrower meaning than flood:

Other hyponyms of flood include flow, deluge, submerge, drench, swamp.

As verbs, flood and inundate are synonyms defined as:

Other synonyms of flood include deluge, swamp.

flood (noun)	inundate (noun)
the act of flooding; filling to overflowing
a large flow
light that is a source of artificial illumination having a broad beam; used in photography
the occurrence of incoming water (between a low tide and the following high tide)
the rising of a body of water and its overflowing onto normally dry land
an overwhelming number or amount

flood (verb)	inundate (verb)
cover with liquid, usually water	fill or cover completely, usually with water
become filled to overflowing	fill quickly beyond capacity; as with a liquid
fill quickly beyond capacity; as with a liquid
supply with an excess of