Rabbit

Also known as a pacemaker; this is a horse with no expected chance of winning but is used to prompt a quick pace on the front end of the race to the benefit of a stablemate who is a closer.

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).

Objection

Claim of foul lodged by a jockey for perceived dangerous or illegal riding by a rival.