Impost
Weight carried or assigned.
in foal
Pregnant mare.
in hand
Running under moderate control, at less than top speed.
in the money
A horse that finishes first, second or third.
infield
Area encompassed by the inner rail of the racetrack.
inquiry
Reviewing the race to check into a possible infraction of the rules. Also, a sign flashed by officials on the tote board on such occasions. If lodged by a jockey, it is called an objection.
ITW
Intertrack wagering.