A horse that works in the rodeo, bucking off cowboys.
A bronco, or bronc is a term used in the United States and Canada to refer to an untrained horse. It may refer to a feral horse that has lived in the wild its entire life, but is also used to refer to domestic horses not yet fully trained to saddle, and hence prone to unpredictable behavior, particularly bucking.
Bronco was a Western series on ABC from 1958 through 1962. The program starred Ty Hardin as Bronco Layne, a former Confederate officer who wandered the Old West, meeting such famous people as Wild Bill Hickok, Billy the Kid, Jesse James, Belle Starr and Cole Younger.