babyish(like a baby) adjective [UK: ˈbeɪ.biɪʃ] [US: ˈbeɪ.biɪʃ]
childish(behaving immaturely) adjective [UK: ˈtʃaɪl.dɪʃ] [US: ˈtʃaɪl.ˌdɪʃ]Peter was fed up with childish girls. = Peter estaba harto de niñas pueriles.
puerile(characteristic of, or pertaining to, a boy or boys) adjective [UK: ˈpjʊə.raɪl] [US: pjuː.ˈriːl]