v. 1
To discolor, as by spilling or other contact with a fluid or substance.
armour stained with blood
v. 2
To taint or tarnish someone's character or reputation
n. 1
A discolored spot or area caused by spillage or other contact with certain fluids or substances.
n. 2
A blemish on one's character or reputation.

Related words

Word family: stainless
Phrases: port-wine stain shit stain blue stain coffee stain effect green stain sap stain stain lifter stain remover

Forms

Plural: stains → greases, dirts, filths, marks…
Past participle: stained
e.g. stained → smeared, blotted, tarnished, color'd…

Stain, Blot, Flaw or Taint?

In the moral sense, we speak of a blot or stain upon reputation; a flaw or taint in character.

J. C. Fernald, English Synonyms and Antonyms (1914)

Use in printed books, per decade from 1850 to 2019.

3 letters: dye¹, hue¹, elt
4 letters: mark¹, spot¹, soil¹, ruin², dirt¹, foil¹, blur¹, tint¹, slur¹, blot¹, smut¹, suss¹, clat
5 letters: color², brand¹, dirty², paint¹, shade¹, grain¹, smear¹, filth¹, sully², grime¹, taint¹, speck¹, tinge¹, fleck¹
6 letters: colour², grease¹, stigma², grunge¹, darken², smudge¹, defile, smooch¹, blotch¹, smouch, dirten, bedaub
7 letters: corrupt², tarnish², blemish², pollute², blacken², splotch, bedizen³
8 letters: disgrace², discolor³, maculate
9 letters: discolour
11 letters: contaminate⁴
13 letters: discoloration⁵
14 letters: discolouration

The small number after each word is its number of syllables (ruin² = 2 syllables).