High blood pressure: A repeatedly elevated blood pressure exceeding 140 over 90 mmHg. Chronic high blood pressure can stealthily cause blood vessel changes in the back of the eye (retina), abnormal thickening of the heart muscle, kidney failure, and brain damage. No specific cause for high blood pressure is found in 95 percent of patients. Treatment for high blood pressure involves dietary changes, regular aerobic exercise, and medication. There are many types of medications used to treat high blood pressure including diuretics, beta-blockers, blood vessel dilators, and others. Also known as hypertension.