Give someone the bird/the finger
Give someone the bird/the finger (English) — A very vulgar, profane, and rude gesture of extending the middle finger while keeping the others clutched (in the palm). So serious as to provoke serious injury or even death. Often responded to by "Is that your IQ?' meaning '1' as one finger is up. I have seen icon/avatars of this. It is a gesture of ignorance. It means the person has no ability to convey their disapproval in any civil way.