When you have sex with a girl from Philadelphia and you pull out to see another man's semen on your penis.
Man 1: dude! Did you smash that chick from the club last night?
Man 2: yeah, but that hoe gave me a Philly cheese dick. And it wasn't my semen.
When you pull out of your hotel and some other dude's nut is on your penis.
I was rather upset when I pulled out of my girl and had a Philly Cheese Dick.