a commemorative or decorative inscribed tablet, esp one fixed to a wall
an ornamental brooch, esp the badge of an honorary order
a film of mucus on teeth where bacteria multiply: compare tartar (2)
a localized abnormal patch in a body part or on the surface of a body part, often the result of injury or a build-up of mineral deposits
[French plaque from plaquier to lay flat, from early Dutch placken to piece, patch]