B meaning in Sports ?

A bucking horse is any breed or gender of horse with a propensity to buck. They have been, and still are, referred to by various names, including bronco, broncho, and roughstock.

The harder they buck, the more desirable they are for rodeo events. Roughstock breeders have long established strings of bucking horses with broodmares and stallions that have been bred and crossbred to more consistently produce the desired temperaments and athletic ability needed for bareback and saddle bronc competition. Bareback broncs are typically smaller, faster athletes whereas saddle broncs are heavier bodied athletes of great strength and endurance.