Antonyms of adj childish

1 sense of childish

Sense 1
childish, infantile -- (indicating a lack of maturity; "childish tantrums"; "infantile behavior")

INDIRECT (VIA immature) -> mature -- (characteristic of maturity; "mature for her age")

Similarity of adj childish

1 sense of childish

Sense 1
childish, infantile -- (indicating a lack of maturity; "childish tantrums"; "infantile behavior")
       => immature (vs. mature) -- (characteristic of a lack of maturity; "immature behavior")