what is a zero wheeled vehicle called

A zero-wheeled vehicle is not a common term, but according to a list of land vehicles categorized by their number of wheels on Wikipedia, some examples of land vehicles with zero wheels include hovercraft, ice skates, litter (vehicle), pogo stick, ski, sled, snowboard, snowmobile, space hopper, and hoverboard. In the context of a crossword puzzle, the answer to the clue "Zero Wheeled Vehicle" could be "sled" or "unicycle".