infantile /ˈɪnfənˌtajəl/ adjective Learner's definition of INFANTILE
1
[more infantile; most infantile] disapproving : annoying and childish : very silly in a way that is not appropriate or polite孩子气的；幼稚的 2
always used before a noun,
medical : affecting babies or very young children婴儿的；幼儿的