Bolt

A sudden veering to the inside or outside rail, often caused by the horse spooking or shying from something.

Pari-Mutuel

A pool style wagering system, where all money input through betting is divided among those with winning tickets (save for various deductions by the track operators).

Bobble/Stumble

A slip or a duck from a horse trying to leave the starting gates, often caused by the surface giving way under the feet. This can range from a mild misstep to a stumble down to their knees.