Bleeder

A horse that bleeds due to a ruptured blood vessel during a race or workout. The medication Lasix can fix this problem.

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.

Apprentice

A new jockey who has not ridden a certain number of winners in a specified time period.