Medical treatment by stopping muscular twitching or irregular contractions of the muscle fibers; especially, of the heart: Defibrillation of abnormal movements of heart muscles is usually treated with electric shocks delivered in an attempt to restore the normal rhythms of the heart.

Defibrillations are used to apply carefully controlled electric shocks that are administered either through a device on the exterior of the chest wall or directly to the exposed heart muscle, to restart or to normalize the rhythms.