Fig. to reveal one's intentions to someone. (From card games.) I don't know whether Jim is intending to marry Jane or not. He's not one to show his hand. If you want to get a raise, don't show the boss your hand too soon.
to tell people your plans or ideas, especially if you were keeping them secret before
Usage notes: When card players show their hand in a game of cards, they show the other players the cards they are holding, usually because they cannot continue to play the game.
I'm a bit reluctant to show my hand at this stage in the proceedings.