Inbreeding:  Mating of near-related relatives, such as brother and sister, or sire and daughter.

Inside and Outside reins:  A term used to describe the reins as the horse is moving in a circle.  Imagine that you are standing in the center of a ring.  There is someone riding clockwise around you.  The right side of the horse and rider is visible to you.  This is the "inside."  The left side of the horse and rider is visible from the fence.  This is the "outside."  If the horse were to change directions, then the left side would be "inside."