parting shot

noun

1. a threat, insult, condemnation, sarcastic retort, or the like, uttered upon leaving.

noun

1. a hostile remark or gesture delivered while departingAlso called: Parthian shot

A final insult or last word in an argument, as in As she stalked out, Jane hurled as a parting shot, “And I quit!” This idiom apparently originated as a corruption of Parthian shot, referring to the practice of ancient Parthian warriors of turning back to shoot at their pursuers. [Late 1800s]