Abduction: In general, refers to movements moving outward from the center of the body.  Hip abduction is moving the legs, knees and feet outward. Shoulder abduction is moving the arms and hands out to the side.

Abduction, for gymnastics, usually refers to gymnastics/strength training and the specific abductor weight machines or exercises, that are used to increase the flexibility of the legs and strengthen the muscles that pull the legs apart in to a straddle split.