Philly cheese is a verb. It is used to describe a way to inflict pain or in other cases murder your victim, by the process of stabbing them with a small military knife/bowie knife. It is most commonly heard when playing a game of COD Black Ops usually because people find much dissapointment when shanked by other players. However, the term has been used in much real cases and scenarios, including the murder of Julius Ceasar. In summarization to Philly Cheese is to stab someone.
dude i cant believe that guy just came up to me and philly cheesed me in the back causing total humiliation to me.