queen regnant vs adult female

queen regnant and adult female both are nouns.

Word	Noun	Adjective	Verb	Adverb
queen regnant	Yes	No	No	No
adult female	Yes	No	No	No

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

Other hypernyms of queen regnant include female aristocrat, woman.

queen regnant (noun)	adult female (noun)
a female sovereign ruler	an adult female person (as opposed to a man)