Having arrived at maturity, or to full size and strength; matured; as, an adult person or plant; an adult ape; an adult age.
- One who has attained maturity or legal age.
- Biology A fully grown, mature organism.
- Fully developed and mature.
- Relating to, intended for, or befitting adults: adult education.
- Containing or dealing in explicitly sexual material; pornographic: adult movies; adult bookstores.