A snowmobile, also known as a snowmachine (chiefly Alaskan), motor sled (chiefly Canadian), ski-doo (Ontario and Quebec, dated proprietary eponym), motor sledge, skimobile, snow scooter, or simply a sled is a motorized vehicle designed for winter travel and recreation on snow.
Their engines normally drive a continuous track at the rear, while skis at the front provide directional control. The earliest snowmobiles were powered by readily available industrial four-stroke, air-cooled engines. These would quickly be replaced by lighter and more powerful two-stroke gasoline internal combustion engines and since the mid-2000s four-stroke engines had re-entered the market.