Backwards Snap Back (BSB) pertains to a snap back hat. this is traditionally worn forwards, however a BSB is turned backwards with the bill to the back. It is the headwear of choice for dudebros, aspiring iTunes rappers, and tools in general.
Peep that gymbro hitting bench press with a BSB. He had to sit hella far back for his bill to clear the bench. This place is turning into a tool shed.