"A stab in the back" is a phrase used to describe an act of betrayal or treachery. There are several synonyms that can be used to convey similar meanings. One such synonym is "backstabbing," which refers to someone conniving behind one's back in order to cause harm or damage. Another synonym is "treason," which denotes a betrayal of one's country or principles. Other possible synonyms include "double-crossing," "betrayal," "disloyalty," and "perfidy." Regardless of the word used, the underlying meaning remains the same - a sense of hurt and disappointment that comes from being betrayed by someone who was trusted.