In the money
A horse finishing first, second or third is "in the money."
Infield
The area within the inner rail of a racetrack.
Inquiry
An inquiry is a review of a race to determine if there has been an infraction of the rules. Officials will flash the inquiry light on the tote board on such occasions. If a jockey claims a rules infraction, it is called an objection.
Irons
The stirrups are referred to as irons.