card up 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. They think they have an airtight case against me, but I've got a card or two up my sleeve. I figured the defense attorney had a card up her sleeve, and here it is—a new eye-witness.
Farlex Dictionary of Idioms. © 2022 Farlex, Inc, all rights reserved.
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.
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.