What is "cardsharks"

Usage examples of "cardsharks".

But because their hair was hidden under dark hats and their faces were obscured behind stockings and bandannas, and also because each robber was obviously putting on an act and an accent with his voice (not to mention the fact that the cardsharks, from Bruno Martinez through to Bud Gleason,- were shitting ice cubes), it was difficult to say just which local personalities were responsible for this outrage.