Rabbit
A speed horse running as an entry with another, usually come-from-behind horse. The rabbit is expected to set a fast pace to help the chances of its stablemate.  

Racing Secretary
Official who drafts conditions of races and assigns weights for handicap events.  

Rail
The barrier on either side of the racing strip. Sometimes referred to as the "fence."  

Rail Runner
Horse that prefers to run next to the inside rail.  

Rank
A horse that refuses to settle under a jockey's handling in a race, running in a headstrong manner without respect to pace. 

Receiving Barn
Structure used by horses shipping in for a race who do not have a stall at that racetrack.

Refuse
1) When a horse will not break from the gate. 2) In jumping races, balking at a jump. 

Reins
Long straps, usually made of leather, that are connected to the bit and used by the jockey to control the horse.  

Reserved
1) Held for a particular engagement or race. 2) Held off the pace.  

Ridden Out
A horse that finishes a race under mild urging, not as severe as driving.