Definition of "impetus"

impetus

/ˈɪm.pə.təs/

noun
plural impetuses
1. Anything that impels; a stimulating factor.
  Quotations
  Once set a strong mind thinking, and you have done all that it needs for its education. It matters little what is the first impetus, so that it only be set to work.
  1838 (date written), L[etitia] E[lizabeth] L[andon], chapter VI, in Lady Anne Granard; or, Keeping up Appearances. […], volume I, London: Henry Colburn, […], published 1842, page 64
  In a single moment Montenegro and their supporters were given fresh impetus and encouragement. Beciraj tested Hart with a low shot before teenager Phil Jones, on his England debut, suffered an anxious moment when Stevan Jovetic went down under his challenge, leaving the youngster clearly relieved to see referee Stark wave away Montenegro's appeals.
  2011, Phil McNulty, Euro 2012: Montenegro 2-2 England‎
2. A force, either internal or external, that impels; an impulse.
3. The force or energy associated with a moving body; a stimulus.
4. (history, medieval physics) A principle of motive force, held as exquivalent to weight times velocity by John Buridan, in an auxiliary theory of Aristotelian dynamics introduced by John Philoponus, describing projectile motion against gravity as linear until it transitions to a vertical drop and the intellectual precursor to the concepts of inertia, momentum and acceleration in classical mechanics.
5. An activity in response to a stimulus.