catch someone napping
US /kætʃ ˈsʌm.wʌn ˈnæp.ɪŋ/
UK /kætʃ ˈsʌm.wʌn ˈnæp.ɪŋ/

1.
pillar a alguien desprevenido, sorprender a alguien
to surprise someone when they are not prepared for something, especially when they are not paying attention or are doing something they shouldn't be doing
:
•
The teacher caught him napping when he was playing games on his phone during class.
El profesor lo pilló desprevenido cuando estaba jugando en su teléfono durante la clase.
•
The sudden inspection caught many employees napping, as they were not following company protocols.
La inspección repentina pilló a muchos empleados desprevenidos, ya que no estaban siguiendo los protocolos de la empresa.