愚ぐ鈍どん

na-adjective, noun

stupid; dim-witted; dull

Describes a person or their thinking as slow, lacking sharpness, or unintelligent. Often used critically or self-deprecatingly. Not a casual slang term; carries a somewhat formal or literary tone.

• 彼かれは愚ぐ鈍どんな顔かおつきをしているが、実じつはとても頭あたまが切きれる。

  He has a dull-looking face, but he's actually very sharp.

• そんな愚ぐ鈍どんなミスをするなんて、自じ分ぶんが情なさけない。

  I'm ashamed of myself for making such a stupid mistake.