Definition of "immature" in English

adjective

1. (now rare) Occurring before the proper time; untimely, premature (especially of death).

2. Not fully formed or developed; not grown.

3. Childish in behavior; juvenile.

   • You're only young once, but you can be immature the rest of your life.
   • The man was immature for throwing a tantrum.
   • Wilhelm Stekel - As quoted in The Catcher in the Rye (1951) by J. D. Salinger. The mark of the immature man is that he wants to die nobly for a cause, while the mark of a mature man is that he wants to live humbly for one.

noun

1. An immature member of a species.