The term "All-Terrain Vehicle" or ATV is used in a general sense to describe any of a number of small open motorized Buggy and tricycles designed for off-road use. However, the American National Standards Institute (ANSI) defines an ATV as a vehicle that travels on low pressure tires, with a seat that is straddled by the operator, and with handlebars for steering control. By the current ANSI definition, it is intended for use by a single operator, although a change to include 2-seaters (in tandem) is under consideration.
The rider sits on and operates these vehicles like a motorcycle, but the extra wheels give more stability at slow speeds. Although typically equipped with three or four wheels, six-wheel models exist for specialized applications. Engine sizes of ATVs currently for sale in the United States (as of 2007) range from 50cc to 800cc.
Four wheeled versions are most commonly called "quads," "four-wheelers" or "ATVs" in the United States and Canada, and "quad bikes" or "quad cycles" in other English-speaking countries. In Australia, ATVs are also known as "forbys". Models with three wheels are typically known as "three-wheelers," and ATCs (or less commonly "All-Terrain Cycles" and "trikes").
ATVs can also be considered Off Highway Vehicles (OHV) or Off Road Vehicles (ORV), along with motorcycles, Jeeps and other off-road capable machines.