The definition of a trifecta, also called a triple, is type of bet in which someone wins if they correctly guess the 1st, 2nd and 3rd place winners of a race.(noun)
An example of a trifecta is naming all three top finishers of a horse race.
See trifecta in Webster's New World College Dictionary
Origin: tri- + (per)fecta
See trifecta in American Heritage Dictionary 4
Origin: + (per)fecta.