Based on the review of various understandings of the leapfrogging, a rigid and measurable definition of technology leapfrogging is presented by using the method of concept replacement in the field of the analytical philosophy and the classical analytic tool in the technology management theory, that is, technology S curve. This definition makes measuring the scale of technology leapfrogging possible. Based on the definiton, a series of problems, such as precondition for technology leapfrogging, planning of technology leapfrogging, evaluating technology leapfrogging, could be all studied easily.