1. not mature, ripe, developed, perfected, etc.
  2. emotionally undeveloped; juvenile; childish.
  3. Physical Geography. youthful(def 5).
  4. Archaic. premature.


  1. not fully grown or developed
  2. deficient in maturity; lacking wisdom, insight, emotional stability, etc
  3. geography a less common term for youthful (def. 4)

1540s, “untimely, premature,” from Latin immaturus “untimely, unripe,” from assimilated form of in- “not, opposite of” (see in- (1)) + maturus (see mature (v.)). In 16c., usually in reference to early death; modern sense of “not fully developed” first recorded 1640s. In reference to mentalities or behaviors not considered age-appropriate, from 1920.


  1. Not fully grown or developed.
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