An upset occurs in a competition, frequently in electoral politics or sports, when the party popularly expected to win (the favorite), is defeated by an underdog whom the majority expects to lose, defying the conventional wisdom. The underdog then becomes a giant-killer.The meaning of the word has sometimes been erroneously attributed to the surprising defeat of the horse Man o' War by the horse Upset (the loss was the only one in Man o' War's career); in fact, the term pre-dates that 1919 race by at least several decades. In its sports coverage immediately following Upset's victory, the Washington Post wrote, “One might make all sorts of puns about it being an upset.”