noun

1. 1. an impelling, or driving forward with sudden force
   2. an impelling force; sudden, driving force; push; thrust; impetus
   3. the motion or effect caused by such a force
2. 1. incitement to action arising from a state of mind or some external stimulus
   2. a sudden inclination to act, usually without premeditation
   3. a motive or tendency coming from within prompted by an impulse of curiosity
3. Elec. a momentary surge in one direction of voltage or current
4. Mech. the change in momentum effected by a force, measured by multiplying the average value of the force by the time during which it acts
5. Physiol. the progressive wave of excitation over a muscle or nerve fiber, which causes or inhibits activity in the body

Etymology: L impulsus < pp. of impellere: see impel