What is a “dead heat” in horse racing?

A dead heat means that two horses in a race tie for a placing, no matter where they finish. It’s possible to have a dead heat for seventh, for instance, though it would have no impact on the wagering.  

Finishes in a horse race were originally decided by the eyes of the judges and later with photography. But in recent years high-definition cameras and technology allow the judges to separate horses by a few whiskers at the finish line.

But sometimes it’s still not possible to separate two finishers, in which case a dead heat is declared.

When that happens, affected betting pools are divided in half and distributed to backers of both horses.