A bet which is more than standard for a particular situation.(noun)
To bet an amount which is more than standard for a particular situation.(verb)
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Use "overbet" in a sentence
"We were led to this research by an age-old racetrack puzzle economists call the “favorite-longshot bias”: horse bettors historically have overbet long shots, and they win less often than their odds suggest."
"In essence, people tend to overbet unlikely outcomes."
"This is precisely the kind of suicidal overbet that a player like Reategui inspires."