Definition
Defibrillator: A device that delivers an electric shock to help restore a normal heart rhythm in certain life-threatening rhythm disorders.
A defibrillator delivers a controlled electric shock through the chest to help the heart return to a normal rhythm in certain life-threatening rhythm disorders.
Defibrillators in ambulances and hospitals usually also display the heart rhythm on a screen and are used by trained medical staff.
The type found in public places that guides the user with voice prompts is called an automated external defibrillator (AED).