The Collaborative International Dictionary of English v.0.48:

Stain \Stain\, v. i.
   To give or receive a stain; to grow dim.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Stain \Stain\ (st[=a]n), v. t. [imp. & p. p. Stained
   (st[=a]nd); p. pr. & vb. n. Staining.] [Abbrev. fr.
   distain.]
   1. To discolor by the application of foreign matter; to make
      foul; to spot; as, to stain the hand with dye; armor
      stained with blood.
      [1913 Webster]

   2. To color, as wood, glass, paper, cloth, or the like, by
      processes affecting, chemically or otherwise, the material
      itself; to tinge with a color or colors combining with, or
      penetrating, the substance; to dye; as, to stain wood with
      acids, colored washes, paint rubbed in, etc.; to stain
      glass.
      [1913 Webster]

   3. To spot with guilt or infamy; to bring reproach on; to
      blot; to soil; to tarnish.
      [1913 Webster]

            Of honor void,
            Of innocence, of faith, of purity,
            Our wonted ornaments now soiled and stained.
                                                  --Milton.
      [1913 Webster]

   4. To cause to seem inferior or soiled by comparison.
      [1913 Webster]

            She stains the ripest virgins of her age. --Beau. &
                                                  Fl.
      [1913 Webster]

            That did all other beasts in beauty stain.
                                                  --Spenser.
      [1913 Webster]

   Stained glass, glass colored or stained by certain metallic
      pigments fused into its substance, -- often used for
      making ornamental windows.
      [1913 Webster]

   Syn: To paint; dye; blot; soil; sully; discolor; disgrace;
        taint.

   Usage: Paint, Stain, Dye. These denote three different
          processes; the first mechanical, the other two,
          chiefly chemical. To paint a thing is to spread a coat
          of coloring matter over it; to stain or dye a thing is
          to impart color to its substance. To stain is said
          chiefly of solids, as wood, glass, paper; to dye, of
          fibrous substances, textile fabrics, etc.; the one,
          commonly, a simple process, as applying a wash; the
          other more complex, as fixing colors by mordants.
          [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Stain \Stain\, n.
   1. A discoloration by foreign matter; a spot; as, a stain on
      a garment or cloth. --Shak.
      [1913 Webster]

   2. A natural spot of a color different from the gound.
      [1913 Webster]

            Swift trouts, diversified with crimson stains.
                                                  --Pope.
      [1913 Webster]

   3. Taint of guilt; tarnish; disgrace; reproach.
      [1913 Webster]

            Nor death itself can wholly wash their stains.
                                                  --Dryden.
      [1913 Webster]

            Our opinion . . . is, I trust, without any blemish
            or stain of heresy.                   --Hooker.
      [1913 Webster]

   4. Cause of reproach; shame. --Sir P. Sidney.
      [1913 Webster]

   5. A tincture; a tinge. [R.]
      [1913 Webster]

            You have some stain of soldier in you. --Shak.
      [1913 Webster]

   Syn: Blot; spot; taint; pollution; blemish; tarnish; color;
        disgrace; infamy; shame.
        [1913 Webster]

WordNet (r) 3.0 (2006):

stain
    n 1: a soiled or discolored appearance; "the wine left a dark
         stain" [syn: stain, discoloration, discolouration]
    2: (microscopy) a dye or other coloring material that is used in
       microscopy to make structures visible
    3: the state of being covered with unclean things [syn: dirt,
       filth, grime, soil, stain, grease, grunge]
    4: a symbol of disgrace or infamy; "And the Lord set a mark upon
       Cain"--Genesis [syn: mark, stigma, brand, stain]
    5: an act that brings discredit to the person who does it; "he
       made a huge blot on his copybook" [syn: blot, smear,
       smirch, spot, stain]
    v 1: 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"
    2: produce or leave stains; "Red wine stains the table cloth"
    3: make dirty or spotty, as by exposure to air; also used
       metaphorically; "The silver was tarnished by the long
       exposure to the air"; "Her reputation was sullied after the
       affair with a married man" [syn: tarnish, stain,
       maculate, sully, defile]
    4: color for microscopic study; "The laboratory worker dyed the
       specimen"

Moby Thesaurus II by Grady Ward, 1.0:

259 Moby Thesaurus words for "stain":
   apply paint, aspersion, attaint, badge of infamy, bar sinister,
   bastardize, baton, bedaub, bedizen, begild, bend sinister, besmear,
   besmirch, besmoke, besmutch, besoil, bespatter, bestain, birthmark,
   black, black eye, black mark, blacken, blaze, blaze a trail,
   blemish, bloodstain, blot, blotch, blow upon, blur, brand,
   broad arrow, brush on paint, brutalize, calcimine, caste mark,
   censure, chalk, chalk up, champain, check, check off, checkmark,
   chromogen, cicatrix, cicatrize, coat, coat of paint, coating,
   color, color filter, color gelatin, colorant, coloring, complexion,
   contaminate, corrupt, cover, cut, dab, dapple, darken, dash, daub,
   dead-color, debauch, deep-dye, defame, defect, defile, define,
   delimit, demarcate, demoralize, deprave, dip, dirty, disapprove,
   discolor, discoloration, disgrace, disparage, disparagement,
   distemper, dot, double-dye, drier, dye, dyestuff, earmark,
   emblazon, enamel, engild, engrave, engraving, expose,
   expose to infamy, exterior paint, eyesore, face, fast-dye,
   flat coat, flat wash, flaw, fleck, flick, floor enamel, flyspeck,
   freckle, fresco, gash, gibbet, gild, glaze, gloss, grain, graving,
   ground, hack, hang in effigy, hatch, hue, illuminate, imbue,
   impress, imprint, imputation, ingrain, interior paint, japan, jot,
   lacquer, lay on color, lentigo, line, macula, maculation, macule,
   make a mark, mark, mark of Cain, mark off, mark out, marking,
   medium, mole, mottle, nevus, nick, notch, odium, onus,
   opaque color, paint, parget, patch, pencil, pepper, pervert,
   pigment, pillory, pillorying, point, point champain, polka dot,
   prick, prime, prime coat, primer, priming, print, punch, punctuate,
   puncture, reflection, reprimand, reproach, riddle, ruin, scar,
   scarification, scarify, scorch, score, scotch, scratch, scratching,
   seal, seam, sear, shade, shadow, shame, shellac, singe,
   slop on paint, slubber, slur, smear, smirch, smoke, smouch, smudge,
   smut, smutch, soil, soilage, soilure, spatter, speck, speckle,
   splash, splatter, splotch, spoil, spot, stamp, stigma, stigmatism,
   stigmatization, stigmatize, stipple, strawberry mark, streak,
   striate, stripe, sully, taint, tar, tarnish, tattoo, tattoo mark,
   tempera, thinner, tick, tick off, tinct, tinction, tincture, tinge,
   tint, tittle, tone, trace, transparent color, turpentine, turps,
   undercoat, undercoating, underline, underscore, varnish, vehicle,
   vilify, wash, wash coat, watermark, whitewash