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.
Exacta
A bet selecting the first and second horses in a race in the correct order. An exacta box refers to paying a little more to ensure they can finish in either order.
Dead Heat
Two or more horses finishing so close at the wire, that they were unable to be separated on a photo finish and deemed to have tied.