WordNet
n. a single bet on two horse races in the same day
Wikipedia
A daily double is a wager offered by horse and dog racing tracks. Bettors wager on the winners of two races, pre-designated by the track for a particular race day. While the Daily Racing Form's glossary defines a Daily Double as two consecutive races, this is a loose rule. Many tracks' Daily Doubles are not consecutive. Because of the increased difficulty of picking two straight winners, winning daily double bets often pay off at high odds.
Usage examples of "daily double".
I'll win the quinella or the daily double and one day we'll go home to my village and I'll take our lands back and plant them again and Chairman Mao will welcome us home and let us take our lands back and we'll live so happily, so rich and so happy.
The labor force was losing, on average, three workers a day, and movie theaters were showing daily double features to provide a fantasy refuge for those without jobs.
Two of his horses even won the daily double at Santa Anita last week, and, along with a few others, are galloping towards millions in stud fees.
In February a year ago he had learned that a Hialeah daily double featured in a sheet called Track Almanac had come through for a killing, and he had subscribed, though the ten bucks a week was a sixth of his salary.