Backdoor, Dickhead Share definition Flag Philly slang for "Please open the Backdoor of the bus, bus driver". often used by teenagers and impatient adults when getting off of the busPhilly Septa Teenage Passenger: BACKDOOR, DICKHEAD!!! Bus Driver: alright. here you go Backdoor, Dickhead by nintengeek March 14, 2019 Get the Backdoor, Dickhead mug.