Off-Road is a stat in Mario Kart Wii and Mario Kart 7. It determines how fast the kart goes if not on the road. Off-Road is anywhere that is not on the main road (water, grass, sand, etc.) but is not out of bounds. In other Mario Kart games, Off-road is determined by the Acceleration stat. Some tracks, such as SNES Mario Circuit 3, have no out of bounds.
Examples of vehicles with high off-road stats in Mario Kart Wii are Tiny Titan, Magikruiser, and Zip Zip. Vehicles with low off-road stats include Flame Flyer and Spear. Large vehicles tend to have lower off-road capabilities, while small karts are better off-road vehicles. There are some exceptions, like the Phantom, which is a large bike which has high off-road stat, and the Blue Falcon, which is a small kart with low off-road stat.