infantile

/ˈɪnfəntaɪl/

/ˈɪnfəntaɪl/

Infantile means immature or childish. Thumb-sucking and temper tantrums are examples of infantile behavior.

Doctors use the word infantile just like you'd expect: to describe things having to do with infants or babies. The rest of us, though, generally use this adjective when someone's being a brat or a crybaby or otherwise behaving immaturely. If someone refers to your sense of humor or your style of argument as "infantile" they are not offering you a compliment. They might be trying to tell you to "grow up."

Definitions of infantile

1. adjective

   of or relating to infants or infancy
   “infantile paralysis”
2. adjective

   being or befitting or characteristic of an infant
   “infantile games”

   synonyms:

   immature, young

   (used of living things especially persons) in an early period of life or development or growth
3. adjective

   indicating a lack of maturity
   “infantile behavior”

   synonyms: childish

   immature

   characteristic of a lack of maturity