In contrast to a non-adult or "minor", a legal adult is a person who has attained the age of majority and is therefore regarded as independent, self-sufficient, and responsible. The meaning of ADULT is fully developed and mature : grown-up. How to use adult in a sentence. ADULT definition: 1. a person or animal that has grown to full size and strength: 2. being, involving, or relating…. Learn more. Adults: Created by Ben Kronengold, Rebecca Shaw. With Jack Innanen, Malik Elassal, Lucy Freyer, Amita Rao. A twenty-something ensemble comedy centering on codependent housemates navigating … ADULT definition: a person who is fully grown or developed or of age. See examples of adult used in a sentence. Definition of adult noun in Oxford Advanced Learner's Dictionary. Meaning, pronunciation, picture, example sentences, grammar, usage notes, synonyms and more. As the child grows to become an adult: so far, it has been a consumer, but the growth of a human being lies in his or her capacity to contribute, to be a contributor. Define adult. adult synonyms, adult pronunciation, adult translation, English dictionary definition of adult. n. 1. One who has attained maturity or legal age. 2. Biology A fully grown, mature organism. adj. 1. … Adult is noun and an adjective, both of which refer to something mature, no longer a child. A full-grown person is called an adult: they can vote, rent cars, and choose to eat sugary cereal for dinner every night. 2 days ago · Adjective adult (comparative more adult, superlative most adult) Fully grown. an adult human, animal, or plant