thoroughbred racing(n = noun.act) - the sport of racing thoroughbred horses;
is a kind of horse racing

auto racing, boat racing, camel racing, car racing, dog racing, greyhound racing, harness racing, horse racing, hydroplane racing, racing, racing boat, racing car, racing circuit, racing gig, racing shell, racing skate, racing skiff, racing start, racing yacht, thoroughbred, thoroughbred race