An overpair is a pair of downcards of equal rank (a pocket pair) which are higher than any exposed upcards in a hand of poker.
The most common usage is in a game like Hold 'em, when a player has a pocket pair such as KK, and the flop comes J-8-7. In this case, the player has a pair that is higher than any card on the board, so it is called an overpair.
Overpairs are very good hands, but they are still only one pair, and are easily beaten by players who make better hands. In the example above, any player holding a 9-10 would have the best possible hand (a straight) and would be far ahead of the player with the pocket kings.
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