The Collaborative International Dictionary of English v.0.48:

Stigma \Stig"ma\, n.; pl. E. Stigmas, L. Stigmata. [L., a
   mark, a brand, from Gr. ?, ?, the prick or mark of a pointed
   instrument, a spot, mark, from ? to prick, to brand. See
   Stick, v. t.]
   1. A mark made with a burning iron; a brand.
      [1913 Webster]

   2. Any mark of infamy or disgrace; sign of moral blemish;
      stain or reproach caused by dishonorable conduct;
      reproachful characterization.
      [1913 Webster]

            The blackest stigma that can be fastened upon him.
                                                  --Bp. Hall.
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            All such slaughters were from thence called
            Bartelmies, simply in a perpetual stigma of that
            butchery.                             --Sir G. Buck.
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   3. (Bot.) That part of a pistil which has no epidermis, and
      is fitted to receive the pollen. It is usually the
      terminal portion, and is commonly somewhat glutinous or
      viscid. See Illust. of Stamen and of Flower.
      [1913 Webster]

   4. (Anat.) A small spot, mark, scar, or a minute hole; --
      applied especially to a spot on the outer surface of a
      Graafian follicle, and to spots of intercellular substance
      in scaly epithelium, or to minute holes in such spots.
      [1913 Webster]

   5. (Pathol.) A red speck upon the skin, produced either by
      the extravasation of blood, as in the bloody sweat
      characteristic of certain varieties of religious ecstasy,
      or by capillary congestion, as in the case of drunkards.
      [1913 Webster]

   6. (Zool.)
      (a) One of the external openings of the tracheae of
          insects, myriapods, and other arthropods; a spiracle.
      (b) One of the apertures of the pulmonary sacs of
          arachnids. See Illust. of Scorpion.
      (c) One of the apertures of the gill of an ascidian, and
          of Amphioxus.
          [1913 Webster]

   7. (Geom.) A point so connected by any law whatever with
      another point, called an index, that as the index moves in
      any manner in a plane the first point or stigma moves in a
      determinate way in the same plane.
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   8. pl. (R. C. Ch.) Marks believed to have been supernaturally
      impressed upon the bodies of certain persons in imitation
      of the wounds on the crucified body of Christ. See def. 5,
      above.
      [1913 Webster]

WordNet (r) 3.0 (2006):

stigma
    n 1: the apical end of the style where deposited pollen enters
         the pistil
    2: a symbol of disgrace or infamy; "And the Lord set a mark upon
       Cain"--Genesis [syn: mark, stigma, brand, stain]
    3: an external tracheal aperture in a terrestrial arthropod
    4: a skin lesion that is a diagnostic sign of some disease

Moby Thesaurus II by Grady Ward, 1.0:

177 Moby Thesaurus words for "stigma":
   abscess, androecium, anther, aposteme, aspersion, attaint,
   badge of infamy, bar sinister, baton, bed sore, bend sinister,
   besmirchment, birthmark, black eye, black mark, blain, blaze, bleb,
   blemish, blister, bloodstain, blot, blotch, blur, boil, brand,
   broad arrow, bubo, bulla, bunion, calyx, canker, canker sore,
   carbuncle, carpel, caste mark, censure, champain, chancre,
   chancroid, check, checkmark, chilblain, cicatrix, cold sore,
   corolla, corolla tube, corona, cut, dab, dapple, daub, demerit,
   discoloration, disfigurement, disgrace, dishonor, disparagement,
   dot, earmark, engraving, epicalyx, eschar, eyesore, felon, fester,
   festering, fever blister, fistula, fleck, flick, flyspeck, freckle,
   furuncle, furunculus, gash, gathering, graving, gumboil, gynoecium,
   hack, hemorrhoids, imputation, jot, kibe, lentigo, lesion, macula,
   maculation, macule, mark, mark of Cain, marking, megasporophyll,
   microsporophyll, mole, mottle, nevus, nick, notch, odium, onus,
   papula, papule, paronychia, parulis, patch, perianth, petal,
   petechia, piles, pillorying, pimple, pistil, pock, point,
   point champain, polka dot, polyp, prick, puncture, pustule,
   receptacle, reflection, reprimand, reproach, rising, scab, scar,
   scarification, score, scotch, scratch, scratching, shame, slur,
   smear, smirch, smouch, smudge, smut, smutch, soft chancre, sore,
   spatter, speck, speckle, splash, splatter, splotch, spot, stain,
   stamen, stigmatism, stigmatization, strawberry mark, sty, style,
   suppuration, swelling, taint, tarnish, tattoo, tattoo mark, tick,
   tittle, torus, tubercle, ulcer, ulceration, wale, watermark, welt,
   wheal, whelk, whitlow, wound