Definition of "adult"

The young not only differs from the adult by the presence of its gills, but its feet are only developed by degrees, and in several genera there are also a deciduous beak and tail, and intestines of a different form

1840, Georges Cuvier, Edward Blyth, Robert Mudie, George Johnston, J.O. Westwood, “The fourth order of reptiles—The batrachians”, in Cuvier's Animal Kingdom‎, page 286

The paws of the adult brown bear, and also their hams, especially when smoked, are considered a great delicacy.

1837, Michael Donovan, Domestic Economy: Human Food, Animal and Vegetable‎, page 86

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.

1973, Marshall Kaplan, Gans, and Kahn, Children and the urban environment (page 21)

Womanhood was achieved at twenty-one, when the female was "adulted"; manhood was fully achieved at twenty-five, […]

1974, Occasional Papers, numbers 42-46, Syracuse University, page 5

The process of adulting children […] overlaps with the process of the uncontrolled infiltration of the media […] into children’s imagination.

2013, Ewa Rewers, The Contradictions of Urban Art, page 84