Definition of plaque
1a
: an ornamental brooch
especially
: the badge of an honorary order
b
: a flat thin piece (as of metal) used for decoration
c
: a commemorative or identifying inscribed tablet
2a
: a localized abnormal patch on a body part or surface
b
: a sticky usually colorless film on teeth that is formed by and harbors bacteria
c
: an atherosclerotic lesion
d
: a histopathologic lesion of brain tissue that is characteristic of Alzheimer's disease and consists of a dense proteinaceous core composed primarily of beta-amyloid that is often surrounded and infiltrated by a cluster of degenerating axons and dendrites
3
: a clear area in a bacterial culture produced by viral destruction of cells
Buying Guide
Our Reviews team has selected the best electric toothbrushes.
Test Your Vocabulary
Name That Color
-
- Name that color:

Test your knowledge - and maybe learn something along the way.
TAKE THE QUIZ
A daily challenge for crossword fanatics.
TAKE THE QUIZLove words? Need even more definitions?
Merriam-Webster unabridged
Share plaque
Time Traveler for plaque
The first known use of plaque was in 1845
See more words from the same year