plaque

plaque 1 The white, semihardened substance that forms on the teeth as a result of bacterial action on food particles and provides an ideal environment for dental caries (cavities). 2 A semihardened accumulation of substances, including cholesterol, on the inner walls of blood vessels that can lead to blood clot formation, heart attacks, and strokes. 3 In dermatology, a small area of skin that appears different from the surrounding skin and is raised.