What you call an inbred from Philadelphia, played off the word Hillbilly, added with Philadelphia.
Most Philbillies are found in the shittier neighborhoods, Port Richmond, Fishtown, Tacony, and especially Kensington. A Philbilly refers to white trash only, though, so North Philly is not included in this.
If you're stuck in the ghetto, it's just like being stuck in the mountains.
He was drunk at 8 am, his eagles jersey on and sitting on his front porch. He is such a Philbilly.