stain

A discoloured spot or area.

A blemish on one's character or reputation.

A substance used to soak into a surface and colour it.

A reagent or dye used to stain microscope specimens so as to make some structures visible.

Any of a number of non-standard tinctures used in modern heraldry.

To discolour.

“armour stained with blood”

To taint or tarnish someone's character or reputation

To coat a surface with a stain

“the stained glass used for church windows”

To become stained; to take a stain.

To treat (a microscopic specimen) with a dye, especially one that dyes specific features

To cause to seem inferior or soiled by comparison.