unchildlike

/ʌnˈtʃaɪldlaɪk/
adjective
  1. Not typical of or suitable for a child; mature, serious, or sophisticated beyond what is expected for a child's age.
    • He spoke with an unchildlike calmness that made the adults listen carefully.
    • Her unchildlike understanding of complex politics surprised everyone.
    • The movie's dark themes felt unchildlike for a cartoon aimed at young audiences.
  2. Lacking the innocence, playfulness, or simplicity associated with childhood.
    • The painting had an unchildlike darkness that disturbed the gallery visitors.
    • Her unchildlike behavior at the playground made the other kids keep their distance.
    • The child's unchildlike expression showed a weariness beyond his years.
Synonyms
What does "unchildlike" mean? | whatsthatwordmean | whatsthatwordmean