stain
noun
a soiled or discolored appearance
“the wine left a dark stain”
(microscopy) a dye or other coloring material that is used in microscopy to make structures visible
the state of being covered with unclean things
a symbol of disgrace or infamy
“And the Lord set a mark upon Cain”
an act that brings discredit to the person who does it
“he made a huge blot on his copybook”
verb
color with a liquid dye or tint
“Stain this table a beautiful walnut color”
“people knew how to stain glass a beautiful blue in the middle ages”
produce or leave stains
“Red wine stains the table cloth”
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”
color for microscopic study
“The laboratory worker dyed the specimen”
Source: WordNet 3.1, Princeton University