noun.
Slang for an emergency T-type spare-wheel for a vehicle. These types of spare
wheels are not very wide. Usually a torus-
like tire affixed to a steel rim. They vaguely resemble the delicacy of the same name.
Not to be confused with a spare, stock wheel. (As normally seen on Jeeps and large SUV type vehicles.) Stock Spares are frequently attached to the rear door (on an SUV). Donuts are a feature of some cars, and are store in a small space in the trunk.
Donuts are very limited in their ruggedness. You can't
go above fifty, and can't
go over bumps or anything interesting on the road.