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)
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.