In horse racing terminology, a trifecta is a parimutuel bet in which the bettor must predict which horses will finish first, second, and third in exact order. The word comes from the related betting term, "perfecta". A trifecta is known as a tiercé in France and Hong Kong and as a tris in Italy.
Trifecta Boxes 
A Trifecta is where any option in a wager can be correct and the player bets the spread. These are effectively betting on every possible outcome of the three contenders and is calculated.
While a trifecta box is only 3 options (so 6 bets in total) this term is sometimes used, incorrectly, for all boxed bets (e.g. 4 options with 24 total bets, etc.),
Other uses 
It is also used to describe a situation when three elements come together at the same time.
See also 
- Devil's Trifecta, the ninth episode of the tenth season of the American police procedural drama NCIS
- Itkowitz, Colby (2010-03-15). "Specter trifecta in DC publication". Morning Call.
|Look up trifecta in Wiktionary, the free dictionary.|
- The dictionary definition of trifecta at Wiktionary