stain

(noun) a soiled or discolored appearance. Synonyms: discoloration, discolouration. Example: "The wine left a dark stain."

(noun) (microscopy) a dye or other coloring material that is used in microscopy to make structures visible.

(noun) the state of being covered with unclean things. Synonyms: dirt, filth, grime, soil, grease, grunge.

(noun) a symbol of disgrace or infamy. Synonyms: mark, stigma, brand. Example: "And the lord set a mark upon cain"--genesis."

(noun) an act that brings discredit to the person who does it. Synonyms: blot, smear, smirch, spot. Example: "He made a huge blot on his copybook."

(verb) color with a liquid dye or tint. Examples: "Stain this table a beautiful walnut color." "People knew how to stain glass a beautiful blue in the middle ages."

(verb) produce or leave stains. Example: "Red wine stains the table cloth."

(verb) make dirty or spotty, as by exposure to air; also used metaphorically. Synonyms: tarnish, maculate, sully, defile. Examples: "The silver was tarnished by the long exposure to the air." "Her reputation was sullied after the affair with a married man."

(verb) color for microscopic study. Example: "The laboratory worker dyed the specimen."