A thoroughbred is a specific breed of horse developed in England over 300 years ago for racing. These horses are famous for their speed, athletic build, and stamina. Every thoroughbred racing today can trace its ancestry back to just three Arabian stallions brought to England in the late 1600s and early 1700s. The most famous thoroughbred race in America is the Kentucky Derby, where these horses race a mile and a quarter around the track.

Breeders keep careful records of every thoroughbred's family tree, similar to how some families maintain detailed genealogies. To be considered a true thoroughbred, a horse must have both parents registered in official breed books. This careful record-keeping has continued for centuries, making thoroughbreds one of the most precisely documented breeds of any animal.

People sometimes use thoroughbred more loosely to describe anything purebred or high-quality, like a “thoroughbred dalmatian” or even a “thoroughbred athlete.” While these uses suggest excellence and pure breeding, they're not technically correct since thoroughbred specifically refers to that one horse breed. When you hear someone described as a thoroughbred, though, it means they're exceptional at what they do, performing with the grace and power of those remarkable racing horses.