plain clothes

US /ˌpleɪn ˈkloʊðz/
UK /ˌpleɪn ˈkloʊðz/
"plain clothes" picture
1.

vêtements civils, tenue de ville

ordinary clothes, not a uniform or special costume

:
The detective was working in plain clothes.
Le détective travaillait en civil.
Security personnel often blend in plain clothes at events.
Le personnel de sécurité se fond souvent en civil lors des événements.