If someone does the dirty on you, they betray you or treat you very badly. There are plenty of people only too ready to make use of a situation like this to do the dirty on somebody they don't like. Note: You can also say that someone does the dirty. Apparently, Scott and the rest had been wanting to sack Joey since 1988. It was only misplaced loyalty that prevented them from doing the dirty there and then. Note: The usual American expression is do someone dirt.