Definition: A defibrillator is a medical device that is used to treat or prevent heart attacks and strokes. It works by delivering electrical current through the body's blood vessels, which can help to stop the heart from beating too fast, thus reducing the risk of complications such as myocardial infarction (heart attack) and stroke. Defibrillators are typically used in emergency situations when an individual has a heart attack or stroke, but they should be used under professional supervision. The term "defibr