Bucking is a movement performed by a horse in which the animal lowers his head and raises his hindquarters into the air, usually while kicking out with his hind legs. If powerful, it may unseat the rider enough so that he falls off.
Ordinary riders need to learn to ride out and correct a simple buck or two, because it is a relatively common form of disobedience. Further, at times, movement akin to bucking is actually required of a horse: Horses that are jumping over an obstacle actually are using almost the same action as bucking when launching themselves into the air, it is simply carried out with advanced planning over a higher and wider distance. The classical dressage movement known as the Capriole is also very similar to the low buck done by a horse when it kicks out with both hind legs.
Bucking, especially if triggered by fear, pain or excitement, is generally a minor disobedience, unless it is strong enough to unseat the rider, at which point it is a dangerous act. If bucking is a premeditated act of the horse and becomes an undesired habit (such as when a horse learns to buck off a rider so that he will no longer have to work), then the horse must be re-schooled by a professional trainer. There have been Olympians who have had to send their horses for re-training by a specialist.
It is important to address the problem of the bucking immediately. Even with good cause, it is a potentially dangerous disobedience that cannot be encouraged or allowed to continue. However, a rider does need to be sure that it is not poor riding that is causing confusion, or a result of poorly-fitting tack that is causing the horse pain. The horse's turn-out schedule should also be assessed, as extra turn-out will give a horse to release his extra energy before the rider gets on. In certain cases (such as a show, when horses are unable to be turned-out for extended periods), longeing the horses for a brief period can help calm him enough so that the rider can get on.
If a horse bucks, the best solution is to use one direct rein to pull the horse's head sideways and up, turning the horse in a small circle. If a rider pulls the horse's head up with both reins, the horse's neck is stronger and the rider is likely to be flipped over the horse's head. By turning the horse sideways, the rider has more leverage and a horse cannot easily buck while turning around. When the horse stops bucking, it must be asked to move forward; a horse also cannot buck very hard while moving forward. Usually a horse gives some warning that it is about to buck by dropping its head, slowing down or stopping, and excessively rounding up in the back (cowboys referred to this as "getting a lump in the back"). To discourage bucking when the rider anticipates it, the rider should ask the horse to move forward or in a circle, raise their hands and the horse's head, and deliberately put the horse into a hollowed-out frame for a moment by sitting back a bit with their heels down, seat deep, and shoulders slightly back. This will help a rider stay in balance if the horse bucks, and the act of deliberately raising the head and hollowing out the horse's back reduces the power and severity of the buck. Certain training aids, such as a gag bit, certain types of martingale or, particularly on ponies, an overcheck, may also discourage bucking.
In a few cases, a horse that cannot be trained not to buck may be sold to a rodeo stock contractor. Ironically, such horses often fetch a high price in the bucking stock world because they are easy to handle on the ground, yet very clever and skilled at unseating riders, thus allowing a cowboy to obtain a high score if he can stay on. At rodeo auctions such as the Miles City Bucking Horse Sale, a spoiled riding horse, particularly one that is powerfully built, will bring a top price and enjoy a long career doing what they have learned to do.
Unfortunately, many other horses that cannot be trained not to buck cannot find a home anywhere and will eventually wind up being sold for horsemeat.