ex·act·a (ĭg-zāk'tə) n. A method of betting, as on a horserace, in which the bettor must correctly pick those finishing in the first and second places in precisely that sequence. Also called perfecta.
[From American Spanish quiniela exacta, exact quiniela (a game of chance), from Spanish exacta, feminine of exacto, from Latin exāctus; see exact.]
1971, from Amer.Sp. perfecta, shortened from quiniela perfecta "perfect quiniela," a bet in horseracing, originally "a game of chance," from O.Sp. quina "game of dice," from L. quini "five each."