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.
See also: catch, nap
Farlex Dictionary of Idioms.

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.
See also: catch, nap, somebody
Farlex Partner Idioms Dictionary
See also:
  • cooking for one
  • drive (one) out of office
  • force (one) out of office
  • force out of office
  • give (one) (one's) head
  • give head
  • give somebody their head
  • give someone their head
  • 1FTR
  • as one door closes, another (one) opens