sharp tongue (plural sharp tongues) (idiomatic) The practice or characteristic of speaking to others in a harsh, critical, or insulting manner. 1819, Washington Irving, Rip Van Winkle: Times grew worse and worse with Rip Van Winkle as years of matrimony rolled on; a tart temper never mellows with age, and a sharp tongue is the only edged tool that grows keener with constant use.