1. 婴儿(期)的;幼儿(期)的
Infantile behaviour or illnesses are typical of very young children.

2. 幼稚的;孩子气的
If you accuse someone or something of being infantile, you think that they are foolish and childish.

1. indicating a lack of maturity

e.g. childish tantrums
infantile behavior

Synonym: childish

2. being or befitting or characteristic of an infant

e.g. infantile games

3. of or relating to infants or infancy

e.g. infantile paralysis