unchildlike

adjective
un·​child·​like | \ ˌən-ˈchī(-ə)l(d)-ˌlīk How to pronounce unchildlike (audio) \

Definition of unchildlike

: not resembling or appropriate to a child or childhood : not childlike an unchildlike seriousness … her sad, unchildlike expression …— Louisa May Alcott

First Known Use of unchildlike

circa 1775, in the meaning defined above

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