Brit. slang for a crappy car, usually a hatchback, driven by a "Barry Boy".
A popular choice of the acned teen as their first "wheels", sheds are often "done up" with bits of nasty body kit, aftermarket exhausts and - in urban settings - a thumping uprated music system.
Shed owners often can't afford to put petrol in their cars so are commonly spotted on Friday
nights meeting other non-driving shed owners in supermarket car parks to exchange advice on the best make of gaffer tape to stop bits of chrome and trim falling off their creations.
See also acronym SOTW (Shed of the Week), a popular spot on the Barry Boys web site.