a card up (one's) sleeve(redirected from card up their sleeve)
a card up (one's) sleeve
A secret plan, idea, or advantage that can be utilized if and when it is required. A reference to cheating at a card game by hiding a favorable card up one's sleeve. She has a card up her sleeve if they ever try to fire her, since she knows about the boss's unscrupulous business practices.
card up one's sleeve
Also, ace up one's sleeve. A hidden or secret advantage or resource, as in Before we make a decision, let's see if management has another card up its sleeve, or You can count on John to have an ace up his sleeve. The practice of storing something in one's sleeve dates from the 16th century, when clothes rarely had pockets. The current term comes from gambling, where a dishonest player might so conceal an ace or other winning card. [Mid-1800s]
card up (one's) sleeve
A secret resource or plan held in reserve: a tough negotiator who had a number of cards up his sleeve.