noun

• Anything that impels; a stimulating factor.
• A force, either internal or external, that impels; an impulse.
• The force or energy associated with a moving body; a stimulus.
• (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.
• An activity in response to a stimulus.