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.

Objection

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

Also Eligible

A horse that is entered but does not draw into the body of the field due to too many entries, and thus is not permitted to start unless there are enough scratches to shrink the field size.