children's action card game for up to eight players.

A 52-card deck is dealt in facedown stacks (which need not be equal), one for each player. Beginning at the dealer's left, each player turns up his stack's top card and places it in the middle of the playing surface; when a jack is turned up, the first to slap it takes the entire centre stack and places it with his own. (In some games it is placed underneath, though it is usually shuffled in with the rest of the player's stack.) Whoever accumulates the entire deck is the winner. A player who runs out of cards may remain in the game to slap jacks and so replenish his stock.

Because the game depends on how quickly players react to seeing the jack, fairness dictates that each player turn up his cards away from himself and that he slap the jack with the same hand used for placing it in the centre. To penalize the overeager slapper who simply hits every upturned card, some games dictate that slapping any card but a jack requires the offender to give up one of his own cards to the player whose card he erroneously slapped.