(To) Stab someone in the back

如果我们按照字面意思翻译这个俚语，可能会发现自己陷入了刑事纠纷中，用刀去刺某个人。然而， 这个俚语表示秘密地背叛并伤害了亲近和相信我们的人，辜负了他们的信任。我们会把这么做的人称为“背后刺客，陷害别人的人”。

"Did you hear that Sarah stabbed Kate in the back last week?"

"No! I thought they were best friends, what did she do?"

"She told their boss that Kate wasn't interested in a promotion at work and Sarah got it instead."

"Wow, that's the ultimate betrayal! No wonder they're not friends anymore."

“你听说上周莎拉背叛了凯特这件事了吗？”

“没有！我以为她们是最好的朋友，她做了什么？”

“她告诉老板凯特对升职不感兴趣，莎拉顶替了她的位置。”

“哇，那是彻彻底底的背叛！怪不得她们绝交了。”