noun. 1. bettering of skill behaviors of one area of the body stemming from use of another area of the body or bodily part. Commonly referred to as cross-education. 2. training workers in various assignments which are not common to the area they specialize in to ensure they are able to supplement for each other whenever unexpected absences happen. 3. with regard to sports, mixing various exercise or sport activities and behaviors to better things like endurance, tone, and weight.