n. an act that brings discredit to the person who does it; "he made a huge blot on his copybook"

n. a soiled or discolored appearance; "the wine left a dark stain"

n. a symbol of disgrace or infamy; "And the Lord set a mark upon Cain"--Genesis

n. the state of being covered with unclean things

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

v. color for microscopic study; "The laboratory worker dyed the specimen"

v. 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"