Upset (horse)

Upset
Sire	Whisk Broom
Grandsire	Broomstick
Dam	Pankhurst
Damsire	Voter
Sex	Colt
Foaled	1917
Country	United States
Color	Chestnut
Owner	Harry Payne Whitney
Earnings	$37,504
Major wins
Sanford Memorial

Upset was notable as the only horse to have ever defeated Man o' War. Man o' War, who won 20 of his 21 starts, faced Upset in the Sanford Memorial at Saratoga Race Course on August 13, 1919. Losing by a nose, Man o' War was, nonetheless, considered the best horse in the race, as he had been fractious at the starting line, left last and was three to four lengths behind the field. He also carried 15 pounds more than Upset. Post-race analysis was that he would have won the race had it been 20 feet (6.1 m) longer. The loss snapped a six-race winning streak by Man o' War.

Upset was owned by Harry Payne Whitney. The two horses met six more times, including in the 1920 Preakness Stakes, with Man o' War victorious every time.

While it is widely believed that the term "upset", referring to a surprising loss, originated with this horse, that is not the case. The use of the word in horse racing dates to at least 1877, and the meaning "to overturn" or "overthrow" appears to be even older.

...
Wikipedia