(Chiefly in pontoon (blackjack)) the action or practice of keeping a mental tally of the cards played in a game in order to gain an (unfair) advantage.
Origin
1930s; earliest use found in The Frederick News.
Definition of card counting in US English:
card counting
noun
(Chiefly in pontoon (blackjack)) the action or practice of keeping a mental tally of the cards played in a game in order to gain an (unfair) advantage.