stain

Short definition from Wiktionary

Noun

1. 1
   A discolored spot or area caused by spillage or other contact with certain fluids or substances.
2. 2
   A blemish on one's character or reputation.
3. 3
   A substance used to soak into a surface and colour it.
4. 4
   A reagent or dye used to stain microscope specimens so as to make some structures visible.
5. 5
   One of a number of non-standard tinctures used chiefly in post-medieval heraldry, especially tenné, murrey, or sanguine.

Verb

1. 1
   To discolor, as by spilling or other contact with a fluid or substance.
2. 2
   To taint or tarnish someone's character or reputation
3. 3
   To coat a surface with a stain
4. 4
   To become stained; to take a stain.
5. 5
   To treat (a microscopic specimen) with a dye, especially one that dyes specific features
6. 6
   To cause to seem inferior or soiled by comparison.