"tarnish" in the noun sense
discoloration of metal surface caused by oxidation
"tarnish" in the verb sense
1. tarnish, stain, maculate, sully, defile
make dirty or spotty, as by exposure to air also used metaphorically
"The silver was tarnished by the long exposure to the air"
"Her reputation was sullied after the affair with a married man"
Source: WordNet® (An amazing lexical database of English)
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