AED (Automated External Defibrillator)

An automated external defibrillator (AED) is a portable electronic device that automatically diagnoses the life-threatening cardiac arrhythmias of ventricular fibrillation and ventricular tachycardia in a patient, and is able to treat them through defibrillation, the application of electrical therapy which stops the arrhythmia, allowing the heart to reestablish an effective rhythm.

American Heart Association:
What Is an Automated External Defibrillator?

University of Arizona Sarver Heart Center:
Learn How to Use an AED