To keep one's plans, intentions, or information secret from everyone else. Refers to holding one's playing cards close to one's chest in a game, so as not to allow other players to see one's hand. We're all curious about what the boss has been discussing in those meetings with the lawyers, but she's been holding her cards close to her chest. Sorry for not being more straightforward about my plans, but I'm holding my cards close to my chest for the time being.