catch someone with their pants down
US /kætʃ ˈsʌm.wʌn wɪð ðer pænts daʊn/
UK /kætʃ ˈsʌm.wʌn wɪð ðer pænts daʊn/

1.
cogliere in flagrante, cogliere impreparato
to discover someone doing something wrong or embarrassing, or to find them unprepared for something
:
•
The boss caught him with his pants down when he was playing games on his computer during work hours.
Il capo lo ha colto in flagrante mentre giocava al computer durante l'orario di lavoro.
•
The sudden inspection caught many employees with their pants down, as they hadn't prepared their reports.
L'ispezione improvvisa ha colto molti dipendenti impreparati, poiché non avevano preparato i loro rapporti.