From Longman Dictionary of Contemporary Englishbabyishba‧by‧ish /ˈbeɪbi-ɪʃ/ adjective DHBSSClike a baby, or suitable for a baby The games were a little babyish for nine-year-olds.
Examples from the Corpus
babyish• I didn't notice it myself but looking at the people at school you think how babyish.• These lent a world-weary cast to a face that might otherwise have been babyish.• They were all turning 4 and they saw drooling as a babyish behavior, something they were proud to be leaving behind. 