grass widower vs adult male

grass widower and adult male both are nouns.

Word	Noun	Adjective	Verb	Adverb
grass widower	Yes	No	No	No
adult male	Yes	No	No	No

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

Other hypernyms of grass widower include man.

grass widower (noun)	adult male (noun)
a man who is divorced from (or separated from) his wife	an adult person who is male (as opposed to a woman)