Zero turn refers to the turning radius. Standard riding mowers, for example, all have some form of a turn radius. Whether it be 6 degrees or 12 degrees, they have some sort of turn radius which means you need more time to turn and determines how wide your turn is, if you will. Zero turn mowers, however, do not have any turn radius whatsoever. That is why they are advertised as “turn on a dime” and is why they are much more maneuverable than regular riding mowers.