plaque

Concise Oxford English Dictionary © 2008 Oxford University Press:
plaque /plak, plɑːk/

▶noun

• 1 an ornamental tablet fixed to a wall in commemoration of a person or event.

• 2 a sticky deposit on teeth in which bacteria proliferate.

• 3 Medicine a small, distinct, typically raised patch on or within the body, caused by local damage or deposition of material.

  ■ Microbiology a clear area in a cell culture caused by the inhibition of growth or destruction of cells.

• 4 a flat counter used in gambling.

– origin C19: from Fr., from Du. plak ‘tablet’, from plakken ‘to stick’.