You eat her food, enjoy her hospitality and then criticize her behind her back.

你吃她的饭菜，享受她的热情款待，然后在背地里却批评她。

《柯林斯英汉双解大词典》

Anne knew very well that her classmates often laughed at her behind her back and called her weirdo.

安妮很清楚，她的同学经常在背后嘲笑她，称她为怪咖。

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She always knows what's going on in class, even when her students are passing notes behind her back.

她总是知道课堂上正在发生的事情，甚至她的学生在其身后传纸条也能知道。

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As she got older, the name-calling was more often behind her back than to her face.

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She was often bad-mouthed (obviously behind her back) by men over whom she had been promoted.

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They all talked about her behind her back, worrying that they were doing something that made her uncomfortable.

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