Atherosclerosis: A process of progressive thickening and hardening of the walls of medium-sized and large arteries as a result of fat deposits on their inner lining.

Risk factors for atherosclerosis include high levels of "bad" cholesterol, high blood pressure (hypertension), smoking, diabetes and a genetic family history of atherosclerotic disease.

Atherosclerosis is responsible for much coronary artery disease (angina and heart attacks) and many strokes.