2. A sudden wish or urge that prompts an unpremeditated act or feeling; an abrupt inclination: had an impulse to run away; an impulse of regret that made me hesitate; bought a hat on impulse.

3. A motivating force or tendency: "Respect for the liberty of others is not a natural impulse in most men" (Bertrand Russell).

4. Electronics A surge of electrical power in one direction.

5. Physics The product obtained by multiplying the average value of a force by the time during which it acts. The impulse equals the change in momentum produced by the force in this time interval.

6. Physiology The electrochemical transmission of a signal along a nerve fiber that produces an excitatory or inhibitory response at a target tissue, such as a muscle or another nerve.