Device used to heat water.
Since hot water can be used as a weapon it is not allowed in many prison settings. Some prisons may have hot water in the day-room but it is not allowed in the cells.
Inmates will connect two wires from any source, TV plugs headphones or even handmade wire from aluminum foil to any 2 separated metal objects, usually metal-plates. By connecting the two wires to the outlet and dropping the stinger in the water the AC current will pass through the water heating it up. It is possible to boil water and with some practice inmates can even make candy with ingredients smuggled out of the culinary.
Sometimes a poorly made stinger will trip the circuit breaker for an entire tier or block causing discontent for both inmates as well as correctional officers.
Stingers are considered contraband in the prison system.
A group of stingers may coordinate in 'sting operations'.
They'll sting you here (heart) and they'll sting you here (crotch/wallet), they'll nick ya smokes and drink ya beer.
What a manky stinger.