Hypertension:  An elevated arterial blood pressure that is usually indicated by an adult systolic blood pressure of at least 140 mm Hg or a diastolic blood pressure of at least 90 mm Hg. It may result in thickening and inelasticity of the arterial walls and hypertrophy of the left heart ventricle. Hypertension is a risk factor for various pathological conditions and cardiovascular events (e.g. heart attack, heart failure, stroke, end-stage renal disease, or retinal hemorrhage).