未成熟 みせいじゅく Meanings Noun, の-adjective immaturity; infancy Antonym: 成熟 (せいじゅく). Kanji 未 not yet. Read as ミ. 成 become. Read as セイ. 熟 ripe. Read as ジュク. Words containing 未成熟 未成熟卵 (みせいじゅくらん) immature ovum Jinuma: Japanese Dictionary · Word lists