fully grown vs brute

fully grown is not a noun while brute is a noun.

Word	Noun	Adjective	Verb	Adverb
fully grown	No	Yes	No	No
brute	Yes	Yes	No	No

fully grown (noun)	brute (noun)
	a living organism characterized by voluntary movement
	a cruelly rapacious person

fully grown (adjective)	brute (adjective)
(of animals) fully developed	resembling a beast; showing lack of human sensibility