cowman vs adult male

cowman and adult male both are nouns.

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

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

cowman: a male hired hand who tends cattle and performs other duties on horseback
adult male: an adult person who is male (as opposed to a woman)

Other hypernyms of cowman include cowhand, cowherd, cowpoke, cowpuncher, puncher, man.

cowman (noun)	adult male (noun)
a male hired hand who tends cattle and performs other duties on horseback	an adult person who is male (as opposed to a woman)