behind closed doors
Fratello Man, hai avuto un duello a porte chiuse?
Brother Man, did you have a duel behind closed doors?
— Ip Man (2008)
È un allenamento a porte chiuse!
It’s a closed-door training session!
— 哪吒之魔童降世 (2019)
Questa è un'udienza a porte chiuse.
This is a closed-door hearing.
— Oppenheimer (2023)