Stroke: The sudden death of brain cells due to lack of oxygen, caused by blockage of blood flow or rupture of an artery to the brain. Sudden loss of speech, weakness, or paralysis of one side of the body can be symptoms. A suspected stroke may be confirmed by scanning the brain with special X-ray tests, such as CAT scans. The death rate and level of disability resulting from strokes can be dramatically reduced by immediate and appropriate medical care. Prevention involves minimizing risk factors, such as controlling high blood pressure and diabetes. Abbreviated CVA. Also known as cerebrovascular accident.