Back-stab is a term used to describe someone who betrays or deceives a friend or colleague, often in a sneaky or underhanded way. There are several synonyms for this term, including: betray, deceive, double-cross, sell out, stab in the back, and two-face. Each of these words describes a different aspect of the treachery that is associated with back-stabbing. Betray and deceive suggest a deliberate and intentional act of betrayal, while double-cross and sell out imply a sense of betrayal for personal gain. Stab in the back and two-face describe the back-stabber themselves, emphasizing their lack of loyalty and trustworthiness. Ultimately, no matter how you describe it, back-stabbing is a hurtful and destructive act that can have serious consequences for those involved.