|Origin:||, past participle of adolescere 'to grow up'|
1 [only before noun]
fully grown or developed:
an adult lion
the adult population
He lived most of his adult life in Scotland.
typical of an adult's behaviour or of the things adults do:
dealing with problems in an adult way
That wasn't very adult of you.
3 [only before noun]
adult films, magazines, etc are about sex or related to sex:
The film is rated R for language and adult themes.