millionaire vs adult male

millionaire and adult male both are nouns.

Word	Noun	Adjective	Verb	Adverb
millionaire	Yes	No	No	No
adult male	Yes	No	No	No

As nouns, adult male is a hypernym of millionaire; that is, adult male is a word with a broader meaning than millionaire:

millionaire: a person whose material wealth is valued at more than a million dollars
adult male: an adult person who is male (as opposed to a woman)

Other hypernyms of millionaire include man, have, rich person, wealthy person.

millionaire (noun)	adult male (noun)
a person whose material wealth is valued at more than a million dollars	an adult person who is male (as opposed to a woman)