1. of, relating to, or characteristic of an infant or infancy
Usage: formal; somewhat archaic
2. immature or childish in behavior or attitude
Usage: formal; often disapproving

Examples

• The painting captured the infantine innocence of the sleeping baby.
• His infantine features made him look much younger than his actual age.
• She dismissed his complaints as infantine whining.
• The novel explores the transition from infantine dependency to adult responsibility.
• His infantine behavior at the meeting embarrassed his colleagues.
• The researcher studied infantine development patterns in the first year of life.