Bounce
A poor race run directly following a career-best or near-best performance.  

Box
A wagering term denoting a combination bet whereby all possible numeric combinations are covered.

Boxed (In)
To be trapped between, behind or inside of other horses.  

Brace (or Bracer)
Rubdown liniment used on a horse after a race or workout.  

Break (a horse)
1) To train a young horse to wear a bridle and saddle, carry a rider and respond to a rider's commands. Almost always done when the horse is a yearling. 2) To leave from the starting gate.  

Break Maiden
Horse or rider winning the first race of its career. Also known as "earning a diploma."  

Breakage
In parimutuel payoffs, which are rounded down to a nickel or dime, the pennies that are left over. Breakage may be used for any of a number of purposes, depending upon a state's rules of racing.  

Breather
Easing off on a horse for a short distance in a race to permit it to conserve or renew its strength.  

Bred
1) A horse is considered to have been bred in the state or country of its birth -- Secretariat was a Virginia-bred. 2) The past tense of "breed."  

Breeder
Owner of the dam at time of foaling unless the dam was under a lease or foal-sharing arrangement at the time of foaling. In that case, the person(s) specified by the terms of the agreement is (are) the breeder(s) of the foal.