A bucking bull is a bull used in rodeo bull riding competition. They are usually a Brahman crossed with another breed, weighing 1,500 pounds or more, selected for their tendency to "leap, plunge and spin" when a human is on its back. Circa mid-20th century breeders began selecting bulls for bad temperament, that would buck when ridden.

Nothing is done to the bulls to "make" them buck; they're going to do that anyway. But a painless, harmless method is employed to encourage this ability and behavior and to give the animal the incentive to buck as hard and effectively as possible. It's accomplished through the use of a specially designed device known as the flank strap.