na-adjective
Describes a child who acts or speaks in a way that seems older than their age, often with a slightly amused or critical tone.
あの子はおませで、大人みたいな口をきく。
That child is precocious and talks like an adult.
おませな小学生が、難しい本を読んでいた。
A precocious elementary school student was reading a difficult book.
noun
precocious child
Refers to a child who is precocious; often used affectionately or with mild surprise.
うちの娘は小さなおませで、いつも大人の会話に加わりたがる。
My daughter is a little precocious child and always wants to join adult conversations.
Derived from the verb ませる (to be precocious) with the honorific prefix お. The kanji spellings are ateji and rarely used.