behind someone's back

US /bɪˈhaɪnd ˈsʌm.wʌnz bæk/
UK /bɪˈhaɪnd ˈsʌm.wʌnz bæk/
"behind someone's back" picture
1.

achter iemands rug om, zonder iemands medeweten

without someone's knowledge or without telling them

:
I can't believe she talked about me behind my back.
Ik kan niet geloven dat ze achter mijn rug over me sprak.
They made the decision behind his back.
Ze namen de beslissing achter zijn rug om.