1. To alter the course of a wave of motion: When energy is refracted, that course of the wave passes into something from another medium; such as, what water does to light entering it from the air.

When anyone refracts light, radio waves, etc. he or she could be measuring the degree of focusing characteristics in a lens or eyes.

2. To alter the appearance of something by viewing or showing it through a different medium: Refracting or deflecting light, for example, from a straight path by turning or bending a wave; such as, a light or a sound wave.
3. Etymology: from Latin refract, the past participle of refringere "to break off, to break back" from frangere, "to break".