oarswoman vs adult female

oarswoman and adult female both are nouns.

Word	Noun	Adjective	Verb	Adverb
oarswoman	Yes	No	No	No
adult female	Yes	No	No	No

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

Other hypernyms of oarswoman include rower, woman.

oarswoman (noun)	adult female (noun)
a woman oarsman	an adult female person (as opposed to a man)