In equine circles, the terms "hot-blooded," "warm-blooded," and "cold-blooded" are used to categorize a horse's temperament, size, and origin. Medium-size horses, including the American quarter horse, Hanoverian, Cleveland bay, and Canadian, are considered warmbloods with a European heritage. They contain a touch of the temper you get from lithe, "hot-blooded" thoroughbreds or Arabians combined with the calm demeanor of "cold-blooded" working horses.