from The American Heritage® Dictionary of the English Language, 4th Edition
- n. Sports An unofficial championship title attained by a horse that wins the three traditional races for a specified category.
- n. Baseball An unofficial championship title achieved by a player who is at the head of the league in batting average, home runs, and runs batted in.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. The feat of leading one's league in three key statistical categories—batting average, home runs, and RBI for hitters; wins, strikeouts, and ERA for pitchers
- n. The three grandest or oldest open championships of the year
- n. The three greatest thoroughbred races of the year restricted to three-year-olds: the Kentucky Derby, Preakness Stakes, and Belmont Stakes
- n. The three greatest thoroughbred races of the year restricted to three-year-olds: the 2,000 Guineas Stakes, Derby Stakes (aka "Epsom Derby"), and St. Leger Stakes
- n. The three greatest thoroughbred races of the year restricted to three-year-olds: the Queen's Plate, Prince of Wales Stakes, and Breeders' Stakes
- n. Victory by one of the Home Nations — England, Ireland, Scotland, Wales — over the other three in the annual Six Nations Championship.
Sorry, no etymologies found.