Definition of "adult" in English

noun

1. An animal that is full-grown.

2. A person who has reached the legal age of majority.

adjective

1. Fully grown.

   • an adult human, animal, or plant

2. Intended for or restricted to adults rather than children due to size, maturity, knowledge level, judgement, etc.

   • adult clothes; adult cereal; an adult documentary
   • In May 1967 the WGBH Education Division submitted an initial proposal to HUD for a series of four adult television documentaries on conservation in an urban environment.

verb

1. (intransitive, slang) To behave like an adult.

   • Adulting is hard!

2. (nonstandard, rare) To (cause to) be or become an adult.