catch somebody napping
catch (one) napping
1. Literally, to discover that one is sleeping when one is not supposed to be. A: "Why was Bill fired?" B: "I heard they caught him napping at his at his desk."
2. By extension, to exploit or capitalize on one's inattention. We were able to sneak into the building because we caught the security guard napping. I scored a goal after I caught their defenseman napping.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
catch somebody ˈnapping(informal) find somebody not prepared or not paying attention, and perhaps gain an advantage over them as a result: Chelsea’s defence was caught napping in the final moments of the game when Jones scored his second goal for Liverpool.
Nap means ‘sleep’, usually for a short time and especially during the day.
Farlex Partner Idioms Dictionary © Farlex 2017