tarnish

noun

1. (uncountable, usually)Oxidation or discoloration, especially of a decorative metal exposed to air.

   “1918, Hannah Teresa Rowley, Mrs. Helen Louise (Wales) Farrell, Principles of Chemistry Applied to the Household Precipitated calcium carbonate, a very fine powdery form, is used as a basis for many tooth powders and pastes. As whiting it finds a wide use in cleaning metals of their tarnishes.”

   “Limiting the use of silver to special occasions might invite tarnish unless the pieces are carefully protected.”

verb

1. (intransitive)To oxidize or discolor due to oxidation.

   “Careful storage of silver will prevent it from tarnishing.”

2. (transitive)To compromise, damage, soil, or sully.

   “He is afraid that she will tarnish his reputation if he disagrees with her.”

   “I have next shown you the Greeks, and " the wisdom" of their philosophy, often travesting, sometimes tarnishing the Christian religion : […]”

   “The greed that many players show tarnishes the game.”

   “There are normally anti-embarrassment clauses in such arrangements and, from a corporate social responsibility point of view, the upside of standing by a tarnished individual is often outweighed by the downside.”

3. (figuratively, intransitive)To lose its lustre or attraction; to become dull.

   “Till thy freſh Glories, vvhich novv ſhine ſo bright, / Grovv Stale and Tarniſh vvith our daily ſight.”

4. To use a sign, image, expression, etc. sufficiently close to a trademarked one that it brings disrepute to it.