29 synonyms for immature such as childish, crude, babyish, and callow. Immature is an adjective, and its antonyms are ripe and mature.
Crude, green, imperfect, incomplete, not mature, not matured, not ripe, raw, undeveloped, unfinished, unformed, unmellowed, and unripe.
Babyish, born yesterday, callow, childish, green, inexperienced, infantile, ingenuous, jejune, juvenile, naive, puerile, unsophisticated, unworldly, and wet behind the ears.