Noun

(en noun)

A sheet of paper or cardboard with a written or printed announcement on one side for display in a public place.

(obsolete) A public proclamation; a manifesto or edict issued by authority.

* Howell

All placards or edicts are published in his name.

(obsolete) Permission given by authority; a license.

to give a placard to do something

(historical) An extra plate on the lower part of the breastplate or backplate of armour.

(historical) A kind of stomacher, often adorned with jewels, worn in the fifteenth century and later.

Noun

Any flat, thin piece of metal, clay, ivory, or the like, used for ornament, or for painting pictures upon, as a slab, plate, dish, or the like, hung upon a wall; also, a smaller decoration worn on the person, as a brooch.

A piece of flat metal with a writing on it, attached to a building to remind people of a person or an event

(uncountable) An accumulation of biofilm, or bacteria on teeth.

(uncountable, medicine) Atheroma, an accumulation in artery walls made up of macrophage cells and debris containing lipids, (cholesterol and fatty acids), calcium, and connective tissue.

* {{quote-magazine, year=2013, month=July-August, author= Stephen P. Lownie], [http://www.americanscientist.org/authors/detail/david-m-pelz David M. Pelz

, magazine=(American Scientist), title= Stents to Prevent Stroke , passage=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.}}

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