Minus Pool

A pari-mutuel pool – typically a show pool - where one horse is so heavily bet that after deductions there is not enough money left to cover the prescribed minimum on each bet.

Underlay

A horse that is going off at lower odds than it deserves based on performance.

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.