Gallop:  A springing, three-beat gait in which the feet hit the ground in the following order (on a left lead):  left foreleg, right hind leg, and simultaneously the left hind and right forelegs.  In the racer's extended gallop, there is a moment when all four of the horse's feet are off the ground.  One such sequence can cover up to 24 feet.

Gaskin:  That part of the hind leg between the stifle (knee) and the hock (heel).  Named, presumably because of sameness of position, from the obsolete, dialectal English word galligaskins, meaning gaiters or leggings.

Gelding:  A castrated (neutered) male horse.  According to one source, most male horses in the U.S. are geldings; only horses intended for breeding are maintained as stallions.

Get:  A foal, the offspring of a mating; also, all the offspring of a particular stallion (this is always his get, never his gets).

Girth:  A leather or fabric belt used to keep the saddle on the horse's back.  The girth attaches to both sides of the saddle under the belly of the horse.

Grade:  A halfbred horse.  See also crossbred.

Grand Prix:  The highest level of competitive show jumping.

Green:  An untrained horse.

Gymkhana:  Show where mounted games and races (eg. barrel-racing and keyhole) are held.