Im'pe-tŭs, n.

n. [Lat., from impetere, to rush upon, attack, from prefix im, for in, and petere, to fall upon.] 1. Force of motion; the force with which any body is driven or impelled; momentum. ☞ Impetus, like momentum, is measured by the product of mass into velocity. But momentum is the technical term, impetus its popular equivalent, yet differing from it as applied commonly to bodies moving or moved suddenly or violently, and indicating the origin and intensiveness of the motion, rather than its quantity or effectiveness. 2. (Gun.) The altitude through which a heavy body must fall to acquire a velocity equal to that with which a ball is discharged from a piece.