멍청한 in English:

I think it is best not to be impolite.

It's impolite to stare at people.

It's very impolite of you to decline her invitation.

I wanted to ask Tom how much he paid for his new house, but Mary told me that would be impolite.

The new shop assistant was impolite to customers.

Tom apologized to Mary for his son's impolite remarks.

They consider it impolite to disagree with someone they don't know very well.

It is impolite to elbow one's way through the crowd.

He is so impolite that everyone hates him.

Otherwise, it is considered impolite to pass food with the left hand, because the left hand is used for bathing.

she was very impolite

It would be impolite to leave the party so early.

You can't leave without saying goodbye. It's impolite.

I thought he made a very impolite remark.

This functionary is impolite.