have a sharp tongue
To have a tendency to speak maliciously or critically. A: "He has such a sharp tongue that I hate to be around him." B: "Of course you do—who wants to be verbally attacked all the time?"
have a sharp ˈtongue
(informal) (of a person) often speak in an unkind or unpleasant way: You’ve got to be careful of her, she’s got a sharp tongue. ▶ sharp-ˈtongued adj.: a sharp-tongued old man