The term overbet in poker usually describes a bet that is over the size of the pot. Although players are allowed to bet as much as they want in the No Limit format, it is common to size your bets in relation to the size of the pot, with a really big bet being equal to the size of the pot.
Thus, any bet that exceeds the size of the pot is dubbed an overbet.
For example, you could say something like when describing a poker hand: I backed into the nut flush, and I figured he could never put me on that. So, although there was only $200 in the pot, I went for a big overbet and moved all in for $320.
Using an overbet is a legitimate poker strategy, and this move has gained a lot of popularity in recent years, especially in deep-stacked cash games.
