大人おとなじみた

noun-modifying (irregular)

precocious; unchildlike; early-blooming

Describes a child who acts, speaks, or thinks in a way that seems unusually mature for their age. Often carries a slightly negative or critical tone, implying the child is not acting their age.

• あの子こは大人おとなじみたことを言いうね。

  That kid says things that are so grown-up.

• 彼かの女じょはまだ10歳さいなのに、大人おとなじみた考かんがえ方かたをする。

  She's only 10, but she has a very mature way of thinking.