#1 stain v. 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". wn
#2 stain n. [discoloration, discolouration] a soiled or discolored appearance; "the wine left a dark stain". wn
#3 stain n. (microscopy) a dye or other coloring material that is used in microscopy to make structures visible. wn
#4 stain v. produce or leave stains; "Red wine stains the table cloth". wn
#5 stain n. [dirt, filth, grime, soil, grease, grunge] the state of being covered with unclean things. wn
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