n. Having arrived at maturity, or to full size and strength; matured; as, an adult person or plant; an adult ape; an adult age. A person, animal, or plant grown to full size and strength; one who has reached maturity. In the common law, the term is applied to a person who has attained full age or legal majority; in the civil law, to males after the age of fourteen, and to females after twelve.
Under civil law, an infant who, if a boy, has attained his full age of fourteen years, and if a girl, her full age of twelve. In the common law an adult is considered one of full age usually eighteen-years-old (modernly).