widowman vs adult male

widowman and adult male both are nouns.

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

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

Other hypernyms of widowman include man.

widowman (noun)	adult male (noun)
a man whose wife is dead especially one who has not remarried	an adult person who is male (as opposed to a woman)