Definition of "plaque"

(countable) Any flat, thin piece of clay, ivory, metal, etc., used for ornament, or for painting pictures upon, as a dish, plate, slab, etc., hung upon a wall; also, a smaller decoration worn by a person, such as a brooch.  examples

(countable) A piece of flat metal with writing on it, attached to a building, monument, or other structure to remind people of a person or an event.  examples

(countable) A small card representing an amount of money, used for betting in casinos; a sort of gaming chip.  quotations  examples

(countable, biology) A clearing in a bacterial lawn caused by a virus.

(countable, music) In the Hornbostel–Sachs classification system: any flat, thin musical instrument.  examples

(countable, pathology) A broad patch of abnormal tissue distinguishable from surrounding tissue, especially a broad papule (“inflamed, irritated patch”) on the skin.

(countable, uncountable, pathology) An abnormal accumulation of material in or on an organ of the body, often associated with disease.

1. (countable, uncountable, pathology) An accumulation in artery walls made up of macrophage cells and debris containing lipids, (cholesterol and fatty acids), calcium, and connective tissue; an atheroma.  quotations

   Quotations

   • As we age, the major arteries of our bodies frequently become thickened with plaque, a fatty material with an oatmeal-like consistency that builds up along the inner lining of blood vessels. The reason plaque forms isn't entirely known, but it seems to be related to high levels of cholesterol inducing an inflammatory response, which can also attract and trap more cellular debris over time.

     2013 July–August, Stephen P. Lownie, David M. Pelz, “Stents to Prevent Stroke: These Devices can Spring into Shape Automatically to Open Arteries Blocked with Plaque”, in American Scientist‎, New Haven, Conn.: Sigma Xi, the Scientific Research Society, archived from the original on 29 May 2017

2. (uncountable, dentistry) An accumulation of biofilm, or bacteria, on teeth, which may develop into dental calculus (tartar).  examples

3. (countable, medicine) A deposit of beta-amyloid protein occurring in a nerve cell and associated with Alzheimer's disease.  examples