What is English word ADULT?

Definitions of ADULT

1. A fully grown human or animal.
2. A person who has reached the legal age of majority.
3. Fully grown.
4. Intended for or restricted to adults rather than children due to size, maturity, knowledge level, judgement, etc.
5. (intransitive, informal) To behave like an adult.
6. (nonstandard, rare) To (cause to) be or become an adult.