Definitions:

1. Acting in a manner typical of a baby or young child, such as crying, whining, or being overly dependent. ADJECTIVE
   • He was criticized for his babyish reaction to losing the game.
2. Displaying a lack of maturity or behaving in an overly childish way. ADJECTIVE
   • Even as a teenager, he had a tendency to be babyish when he didn't get his way.
3. Having features or qualities that remind one of a baby, such as soft skin, round cheeks, or a gentle demeanor. ADJECTIVE
   • Her babyish smile made her look younger than her actual age.

Synonyms:

• childlike
• immature
• infantile
• youthful