big-girl pants

Noun

 * 1)  Pull-up underwear worn by a girl during and after toilet training, as contrasted to the diapers worn during infancy.
 * 2)  A notional pair of trousers or underwear worn by a female when acting maturely.
 * 1)  A notional pair of trousers or underwear worn by a female when acting maturely.
 * 1)  A notional pair of trousers or underwear worn by a female when acting maturely.
 * 1)  A notional pair of trousers or underwear worn by a female when acting maturely.