| jail |
 | Refers to the requirement that a horse which has been claimed that next runs in a claiming race must run for a claiming price 25 percent higher for the next 30 days. Commonly used in the phrase The horse is in (out of) jail. |
| jockey fee |
| Sum paid to rider for competing in a race. |
| jockey's race |
| A race whose outcome will hinge mostly on strategic thinking by the riders; i.e., one in which riders must pay close attention to pace to keep their horses fresh for a strong finish. |
| jog |
| Slow, easy gait. |
| joint |
| 1) See musculoskeletal system. For injuries, see "Joint Injuries" subsection of "Musculoskeletel System" in veterinary supplement for a more detailed explanation. 2) See battery. |
| joint capsule |
| The structure that comprises the boundary to the joint space. |
| jumper |
| Steeplechase or hurdle horse. |
| juvenile |
| Two-year-old horse. |
