a card game strategy (e.g. blackjack) in which a player keeps a mental tally of the cards played in order to calculate the probability of certain cards being dealt, therefore obtaining an advantage
Card counting is sometimes used to obtain a count of the distribution or remaining high cards in trick-taking games, such as contract bridge or spades.
also card counter , (n.)
The film features a group of pastors who had formed a card-counting team and won millions in Vegas.