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.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
behind somebody’s ˈbackwithout 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
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