A card game was a game played with playing cards.
In 2366, William T. Riker protested Jean-Luc Picard's suggestion that he host negotiations for the Barzan wormhole rather than Picard, as the first officer felt his poker instincts weren't up to snuff. He believed a card game hadn't prepared him for something of great importance. Picard assured him that a game with higher stakes would be more interesting. (TNG: "The Price")