D defs.my
Entry 1 sense Webster, 1913

grownup

· IPA /ɡrˈoʊnˌʌp/
01 adj. fully developed; adult; mature; -- of people and animals; as, Act like a grownup!.
  1. 1.
    fully developed; adult; mature; -- of people and animals; as, Act like a grownup!.