upset
n. countablen. a situation where a person or team wins a game or election that everyone expected them to lose. It can also mean a sudden change that causes trouble or worry.
n. an unexpected result or situation, especially in a sporting or political contest where the underdog defeats the favourite. It may also refer to a physical or emotional disturbance.
The small team caused a huge upset by winning the final.
Political analysts were shocked by the election upset when the newcomer defeated the long-standing incumbent.
While the favourite appeared dominant throughout the season, a series of tactical errors led to a major upset in the championship round, altering the league's power dynamic.
From Middle English upset (“the act of setting up; establishment”), from Middle English upsetten, corresponding to up- + set. Cognate with Middle Low German upset (“setup; arrangement”).
Commonly used with the verb 'to cause' or 'to pull off'.