stab somebody in the back

stab somebody in the ˈback


get, etc. a stab in the ˈback

(informal) do or say something that harms somebody who trusts you; be treated this way: Jane promised to support me at the meeting, but then she stabbed me in the back by supporting David instead. ▶ a ˈback-stabber, ˈback-stabbing nouns: This party is full of back-stabbers.There is always a lot of back-stabbing in academic life.
See also: back, somebody, stab