blackjack, one of the world's most widely played gambling card games; also known as twenty-one or vingt-et-un. Despite contesting claims between the French and Italians, its origins are unknown. Each player receives one card face down and bets that this card plus additional cards dealt face up will beat the dealer's hand without exceeding 21. An ace counts one or eleven, a face card ten, and all others cards according to their face value. A score of 21 on the first two cards is called blackjack.