Hi. Here's a definition I found. Basically just a large military vehicle in service from 1951 to present. From Wikipedia (http://en.wikipedia.org/wiki/M35_2%C2%BD_ton_cargo_truck): "The M35 family of trucks is a long-lived vehicle initially deployed by the United States Army, and subsequently utilized by many nations around the world. A truck in the 2½ ton weight class, it was one of many vehicles in U.S. military service to have been referred to as the "deuce and a half." While the basic M35 cargo truck is rated to carry 5,000 pounds (2,300 kg) off road or 10,000 pounds (4,500 kg) on roads, they have been known to haul twice as much as rated. Trucks in this weight class are considered medium duty by the military and Department of Transportation. The M35 series formed the basis for a wide range of specialized vehicles."