noun

A person who is fully grown or developed.

children should be accompanied by an adult

grown person,grown man,grown woman,grown-up person,grown-up,mature person,mature man,mature woman,person of mature age

adjective

(of a person or animal) fully grown or developed.

the adult inhabitants of the U.S

mature,grown-up,fully grown,full-grown,fully developed,fully fledged,of age,having reached one’s majority

intransitive verb

Behave in a way characteristic of a responsible adult, especially by accomplishing mundane but necessary tasks.