Thoroughbred horse, breed of light horse more properly known as the English running horse. As its name implies, it was the first pedigreed, or "thoroughbred" horse. It originated in England from crosses between imported Turkish and Arabian horses and existing English lines and has since been exported around the world. As the fastest of all horses—it can achieve a speed of just under 40 mi (64 km) per hr for a distance of a mile (1.6 km)—the Thoroughbred has held undisputed reign as king of horse racing (except for the quarter-mile sprint; see quarter horse). Its temperament is racy and nervous. Thoroughbreds average over 16 hands (64 in./160 cm) in height, weigh around 1,100 lb (500 kg), and have a leggy appearance. They may be any color but usually have white markings.
The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2012, Columbia University Press. All rights reserved.