Noun

1. A deep-fried piece of dough or batter, commonly made in a toroidal or ellipsoidal shape, and mixed with various sweeteners and flavors, sometimes filled with jelly, custard or cream.
2. Anything in the shape of a torus
3. a peel-out or skid-mark in the shape of donut; a 360-degree skid.
4. A spare tire, smaller than a full sized tire and is only intended for temporary use.