1) US sprinter 2) Equine sprinter 3) Four-legged racer 4) Muscular mammal 5) Muscular ride 6) Powerful equine 7) Rodeo participant 8) Western cow pony 
See American Quarter Horse.
The Quarter Horse is America's oldest and most popular breed of horse developed during the 17th century from Andalusian, Barb, Arabian and Thoroughbreds introduced by the Spanish and British. The Quarter Horse is a solidly built, small horse standing between 14.3 and 16 hands high and occurs in any solid colour. They are calm and have a well-balanc...
[n] - a small powerful horse originally bred for sprinting in quarter-mile races in Virginia
noun a small powerful horse originally bred for sprinting in quarter-mile races in Virginia
A well-muscled, good-tempered, versatile breed that
one of a breed of strong horses developed in the U.S. for short-distance races, usually a quarter of a mile. · a horse of this breed used in herding livestock.