stupid; dim-witted; dense; dull; obtuse; slow
彼を愚鈍だと決めつけるのは早計だ。
It is hasty to label him as dim-witted.
愚鈍な振りをして相手を油断させた。
He pretended to be dull-witted to catch the opponent off guard.
愚鈍に見えて実は鋭い観察力を持つ。
He looks dim-witted but actually has sharp observation skills.