not mature, ripe, developed, perfected, etc.

emotionally undeveloped; juvenile; childish.

Physical Geography . youthful ( def. 5 ) .

Archaic . premature.

adjective

adult , developed , experienced , grown , mature , old

adjective

adolescent , baby , babyish , callow , childish , crude , green * , half-grown , imperfect , infantile , infantine , jejune , juvenile , kid , kidstuff , premature , puerile , raw , sophomoric , tender * , tenderfoot * , underdeveloped , undergrown , undeveloped , unfinished , unfledged , unformed , unripe , unseasonable , unseasoned , unsophisticated , untimely , wet behind ears , youthful , green , infant , basic , embryonic , fledgling , impubic , inchoate , inexperienced , nouveau , rudimentary , verdant , young