ambassadress vs adult female

ambassadress and adult female both are nouns.

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

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

Other hypernyms of ambassadress include ambassador, embassador, woman.

ambassadress (noun)	adult female (noun)
a woman ambassador	an adult female person (as opposed to a man)