A card higher than any other card or pair. Often used in reference to the community cards in Texas hold 'em(noun)
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Use "overcard" in a sentence
"If you hold a pocket pair and bet into the same card with an overcard (1010 vs. A10) you hold roughly a 65/35 edge."
"Every card on the board is an overcard to your pair, and your only real option is to check-raise and hope your opponent folds, or bet on the turn if he checks the flop."
"Top pair, overcard kicker, and a flush draw . . . excellent."