Behind somebody's back - Idioms by The Free Dictionary
behind somebody's back
behind (one's) back
In one's absence. The phrase typically suggests wrongdoing or deceit. I can't believe you were gossiping about me behind my back! Tom will be upset that we already made the decision behind his back.
behind somebody’s ˈback without somebody knowing, especially because they would not like it: I feel guilty about going behind his back and complaining to the boss. ♢ People were often very rude about her behind her back. OPPOSITE: to somebody’s face
References in periodicals archive
STUNNING news last week, as it emerged that no journalist on Fleet Street has ever said one thing to somebody's face and another behind somebody's back
There is no way on earth that he would go behind somebody's back