backstab

[bak-stab]
verb (used with object), back·stabbed, back·stab·bing.
  1. to attempt to discredit (a person) by underhanded means, as innuendo, accusation, or the like.

Origin of backstab

First recorded in 1920–25; back2 + stab
Related formsback·stab·ber, noun
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018