A moon roof nigger is a person who smokes marijuana with his friend in a
car during the
rain with the windows open, then asks his friends to put the windows up so the rain does not come in; but in order to let the smoke out of the
car he decides to open the moon roof of his
car which contradicts the action of closing the windows to keep the rain from coming in. This person acted like a nigger therefore this person is described as a being a Moon roof nigger.