wealthy man vs nabob

wealthy man and nabob both are nouns.

Word	Noun	Adjective	Verb	Adverb
wealthy man	Yes	No	No	No
nabob	Yes	No	No	No

As nouns, nabob is a hyponym of wealthy man; that is, nabob is a word with a more specific, narrower meaning than wealthy man:

Other hyponyms of wealthy man include nob, toff.

wealthy man (noun)	nabob (noun)
a man who is wealthy	a wealthy man (especially one who made his fortune in the Orient)
	a governor in India during the Mogul empire