Racehorse: Horse bred for racing. Can be Thoroughred, Quarter Horse, Arabian, Standardbred.
Rack: The fifth gait of the American Saddlebred - a flashy four beat gait.
Rainrot: Painful, skin inflammation caused by the Dermatophilus organism, characterized by patches of raised hair and hair loss and crusty exudate.
Rangy: Used to describe a horse with size and scope of movement.
Reining: Type of Western riding in which advanced movements such as spins and slides are executed in various patterns.
Ridgling/Rig: Male horse that has retained one testicle within the body. Can cause stallion-like behavior. Treated with surgury.
Riding Horse: Horse suitable for riding, with the conformation associated with comfortable riding action (as opposed to draft or carriage horses)
Ringbone: Name given to bony changes occurring within the pastern and coffin joints. May be articular or non-articular. Lameness often occurs while changes are occurring but may go away once callosity is completely formed.
Ringworm: Contagious fungal disease characterized by small circular patches in which the hair falls out.
Rising: Used in the UK to describe the age of a horse. For example, a horse approaching four is said to be "rising four". In the US, the term coming is used.
Rising Trot: The action of the rider rising from the saddle in rhythm with the horse's trot. (Also called Posting Trot)
Roach Back: Convex curvature of the spine between the withers and the loins. Opposite of hollow back.
Roached mane: A mane that has been shaved close for its entire length. (See also hogged mane)
Roan: Coat color in which white hairs are mixed with the base coat color. A strawberry roan is where chestnut and white hairs are mixed to give an overall reddish effect. A blue roan refers to a coat in which black and white hairs are mixed, giving an overall blue effect.
Roaring: Characteristic abnormal noise on inhalation, heard in horses with Laryngeal Hemiplegia.
Roman Nose: The convex facial profile seen in Shires and other heavy breeds.
Rosin-back: A broad-backed horse used in the circus for trick riding acts. Rosin is used on the rider's shoes to increase the grip.
Roundworm: Common name for ascarids, an internal equine parasite.