Plaque: a word meaning a flat, plate-like object.

• a plaque in biology is a flat growth-form, as for example,
  • the growth of bacterial colonies on an agar plate
  • a sticky, white film or fluid on the teeth, a mixture of bacteria and food
  • in atherosclerosis, a fat layer inside an artery.

• a flat man-made object, such as a memorial plaque or other flat object