Definition of tween-age in English:

tween-age

(also tween age, 'tween-age, tweenage)

Pronunciation /ˈtwiːneɪdʒ/

noun

informal, rare North American
  • A person who is nearly, or has only just become, a teenager. Also (with the): such people as a class. Compare "tween".

adjective

informal North American
  • Of, relating to, or intended for tweenagers.

Origin

1930s; earliest use found in The Sun. Alteration of teenage after 'tween.