catch someone napping

catch (one) napping

To exploit or capitalize on one's inattention (or, sometimes, literal sleep). 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

catch someone napping

(of an action or event) find someone off guard and unprepared to respond. informal
See also: catch, nap, someone
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