625 ILCS 5/1-101.8: All-terrain vehicle.

Any motorized off-highway device designed to travel primarily off-highway, 50 inches or less in width, having a manufacturer's dry weight of 1,500 pounds or less, traveling on 3 or more non-highway tires, designed with a seat or saddle for operator use, and handlebars or steering wheel for steering control, except equipment such as lawnmowers.