bronc
A wild or half-tamed horse that bucks hard when ridden.
A bronc is a wild or partially tamed horse, especially one that bucks and fights when someone tries to ride it.
In the American West during the 1800s, cowboys had to break broncs by climbing on and staying mounted while the horse jumped, twisted, and kicked, trying to throw them off. This dangerous work required strength, balance, and courage. Today, rodeo riders compete in bronc riding events, where they try to stay on a bucking horse for eight seconds while it does everything possible to unseat them.
When you hear that someone is riding a bronc or breaking a bronc, it means they're dealing with a powerful, spirited animal that hasn't accepted being ridden yet. The challenge isn't just physical: it requires reading the horse's movements and responding instantly. Some horses never fully become tame riding horses and remain broncs their whole lives, too independent and wild-spirited to accept a saddle and rider.