childish
adjective
of, like, or befitting a child.
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
Her thin little chest heaved up and down, and she spoke in a strange, unchildishly fierce way.
From A Little Princess Being the whole story of Sara Crewe now told for the first time by Frances Hodgson Burnett