Definition of long trousers in English:

long trousers

noun

  • Trousers which reach to, or almost to, the ankle.

Phrases

  • boy (or child) in long trousers

    • : an immature person, or one who is behaving in a childish or childlike manner.

  • in long trousers

    • : (as postmodifying phrase) in a more mature, developed, sophisticated, etc., form.

Origin

Mid 18th century. From long + trousers.

Pronunciation

long trousers

/ˌlɒŋ ˈtraʊzəz/