It would probably be a registered [insert breed here]. Thoroughbreds are the most common breed of racehorse, but Arabians, Quarter Horses, Paints, and Appaloosas all race as well.
A steeplechaser
A cheetah or another racehorse.
no
15.3 Hands
Thouroughbred, pure, unmixed, full-blooded, pedigree, pedigreed, pureblooded.
John Henry
After racehorse secretariat
Shergar of Ireland
Kruddler
Racing Plate
Pedigreed
Man o' War