to spoil the appearance of by patches or streaks of color or dirt; discolor; spot
to bring shame upon (someone's character, reputation, etc.); taint; disgrace; dishonor
to change the appearance of (wood, glass, etc.) by applying a dye, pigment, etc.
to treat (material for microscopic study) with a coloring matter that facilitates study, as by making transparent parts visible or by producing a different effect upon different structures or tissues
intransitive verb
to impart or take a color or stain
noun
a discoloration, streak, or spot resulting from staining
a moral blemish; dishonor; guilt; taint: a stain on one's reputation
a substance used to impart color in staining; specif.,
a dye or pigment in solution, esp. one that penetrates a wood surface
a dye used to stain material for microscopic study