1. The altered excitability, conductivity, or electrical condition of a nerve which is produced when a constant electric current is passed through it.
2. A change in the condition of a nerve or a muscle during the passage of a current of electricity.
3. The altered electrical state of an excitable body cell when a constant electric current is passed through it; for example, the changes in membrane potential of excitable cells that cause a passive change in potential at every other point on the body's cell membrane.
4. The transient change of irritability in a nerve or a muscle during the passage of a current of electricity.