Wordnet 3.0
NOUN (1)
1. 
 a bet that you can pick the first and second finishers in the right order; 
[syn: exacta, perfecta]
WordNet (r) 3.0 (2006):
exacta
    n 1: a bet that you can pick the first and second finishers in
         the right order [syn: exacta, perfecta]