Plaque

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