老成 ろうせい Meanings な-adjective, Noun, する verb, Intransitive mature; experienced precocious; mature for one's age Kanji 老 elderly. Read as ロウ. 成 become. Read as セイ. Words containing 老成 老成円熟 (ろうせいえんじゅく) experience that comes with age Jinuma: Japanese Dictionary · Word lists