yachtswoman vs adult female

yachtswoman and adult female both are nouns.

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

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

Other hypernyms of yachtswoman include woman, yachtsperson.

yachtswoman (noun)	adult female (noun)
a female person who owns or sails a yacht	an adult female person (as opposed to a man)