numskull

he acted like a numskull during the meeting.

don't be a numskull; think before you speak.

she called him a numskull for forgetting the appointment.

his numskull behavior cost the team the game.

even a numskull can learn from their mistakes.

don't be such a numskull; just follow the instructions.

he was labeled a numskull for his poor decision-making.

it's numskull moves like that which get people in trouble.

being a numskull won't help you succeed in life.

he realized he was a numskull after making that mistake.