D defs.my
Entry 3 senses Webster, 1913

Impetus

/(ĭm"pē̇*tŭs)/ · Im·pe·tus · IPA /ˈɪm.pə.təs/
01 n. A property possessed by a moving body in virtue of its weight and its motion; the force with which any body is driven or impelled; momentum.
  1. 1.
    A property possessed by a moving body in virtue of its weight and its motion; the force with which any body is driven or impelled; momentum.
  2. 2.
    Fig.: Impulse; incentive; stimulus; vigor; force; as, the President's strong recommendation provided the impetus needed to pass the campaign reform bill.
  3. 3.
    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.(Gun.)