A bronco horse  or a bucking horse is any kind of horse breed that is likely to buck. It's a Spanish word that means rough and it's nowadays used by cowboys to describe untrained or partially trained horses. They are known under various names, including bronco, broncho, and roughstock and are used for different rodeo competitions. In general, the harder they buck the more valuable they are for rodeo events. The most successful bucking horse breeders have established long strings of bucking horses that have been bred and crossbred to more consistently produce the desired temperaments and athletic ability needed for bareback bronc and saddle bronc competitions.