A teenager or tween that behaves like a child. Much like a manchild, but aged around 10 to 19. While their classmates are already thinking about their future and are behaving somewhat maturely, teenchildren are still rather childlike. They may or may not have hit puberty.
Dave: You know what, Roger. It's time to stop being a teenchild and actually STUDY for once.
Roger: Oh shut the fuck up and let me play Sonic the Hedgehog!
by Beanclad October 13, 2018