15% asshole discount

The act of not tipping at a restaurant. The way voluntary tipping policy works, you get to decide what a server gets paid at a restaurant. You don't tip, they don't get payed. Therefor, if you are an asshole, you can get a 15% discount at any restaurant as long as you don't care if the server gets payed for his/her work. (could also be used as the 18% or 20% asshole discount, depending on tipping standards)