Hack:  Well-behaved, well-schooled riding horse of light build.  Some women ride hacks side-saddle.

Half-bred:  Or halfbred; the progeny of a Thoroughbred sire mated with any breed or type of mare or even pony, except a Thoroughbred or Arab.  Also called a grade horse.  According to one source, it is said that over 90 percent of horses in the U.S. are halfbred.  See also crossbred.

Hands:  A measurement term for horses and ponies.  Each hand equals four inches (the average width of a man's hand).  The horse is measured from the ground to the withers (see The Exterior diagram).  If the description says that a horse is 15.2 hh, for example, it means that the horse is 15 hands and 2 inches high (hh means "hands high").  A pony who measures ten hands would be forty inches (or 3 feet, 4 inches) tall at the withers.

Harness racing:  Races, originating in America and Russia, to test speed of Trotters.

Haunches in (travers):  In dressage, the horse moves with head and shoulders parallel to wall and haunches curved toward center of ring.  Outside legs cross over inside legs.

Haunches out (renvers):  In dressage, the horse moves with head and shoulders parallel to wall and haunches curved toward wall.

Heads up:  In hunting, hounds that have lost the scent lift their heads while trying to find it again.

Hit off the line:  In hunting, when hounds regain the scent.

Hock:  The tarsal joint, corresponding to the ankle in man.  From the Anglo-Saxon hoh, meaning heel.

Hollow back:  Exaggerated concavity of the back.

Hoofpick:  A hand-sized, hook-shaped pick used to clean the inside of a horse's hoof.

Hopple:  Harness that restricts movement in any gait but the pace.

Horse:  An equine who measures at least 14.2 hands.  That is:  fourteen hands and two inches.  An animal who measures 14.2 would be 58 inches at the withers, or 4 feet, 8 inches.

Horse show:  A gymkhana with various competitions for dressage, jumping, driving, etc.

Hunt:  The hunting of live game behind the pack of hounds.  Nowadays a drag-hunt, i.e. an artificial "line" is laid across country over (often artificial) fences.

Hunter:  Horse that can gallop cross-country and jump well.  It must be strong and very fit.

Huntsman:  A professional whose duty on the hunt is to find a fox and direct the pack.  He should know and have the affection of each of his hounds and work them skillfully with voice and horn to keep them on the scent.  He also supervises the whippers-in in their job of keeping hounds together.

Hurdler:  Horse that races and jumps hurdles, usually over courses about two and a half miles long.

Hybrid:  The offspring of any cross that involves two different species rather than breeds; the practice is called hybridization.