To bet more money than is usual or sensible in a game, especially in poker.
Overbetting can make people think you are very confident or very foolish, depending on the situation.
Examples:
He overbet and lost all his money.
She overbet on a bad hand and regretted it.
Don't overbet if you don't have a good hand.
He overbet and now he has no money for ice cream.
She always overbets when she's nervous.
He overbet and everyone was surprised.