The Collaborative International Dictionary of English v.0.48:

Astringent \As*trin"gent\ (-jent), a. [L. astringens, p. pr. of
   astringere: cf. F. astringent. See Astringe.]
   1. Drawing together the tissues; binding; contracting; --
      opposed to laxative; as, astringent medicines; a butter
      and astringent taste; astringent fruit.
      [1913 Webster]

   2. Stern; austere; as, an astringent type of virtue.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Astringent \As*trin"gent\, n.
   A medicine or other substance that produces contraction in
   the soft organic textures, and checks discharges of blood,
   mucus, etc.
   [1913 Webster]

         External astringents are called styptics. --Dunglison.
   [1913 Webster]

WordNet (r) 3.0 (2006):

astringent
    adj 1: sour or bitter in taste [syn: acerb, acerbic,
           astringent]
    2: tending to draw together or constrict soft organic tissue;
       "astringent cosmetic lotions" [ant: nonastringent]
    n 1: a drug that causes contraction of body tissues and canals
         [syn: astringent, astringent drug, styptic]

Moby Thesaurus II by Grady Ward, 1.0:

90 Moby Thesaurus words for "astringent":
   Spartan, Spartanic, acerb, acerbic, acid, acidulous, acrid,
   acrimonious, alum, amaroidal, ascetic, asperous, austere,
   authoritarian, biting, bitter, bitter as gall, brisk, caustic,
   clamp, coarse, collapsible, compactable, compressible, compressor,
   constrictor, constringent, consumptive, contractible, contractile,
   contractional, contractive, contractor, cutting, deflationary,
   demanding, double-edged, dour, edged, escharotic, exacting,
   exigent, fierce, foldable, grim, hard, harsh, incisive, inclement,
   irritating, keen, meticulous, mordacious, mordant, mortified,
   nose-tickling, penetrating, piercing, pincer, piquant, poignant,
   puckery, pungent, restorative, rigorous, roborant, rough, rugged,
   scathing, severe, sharp, sour, stabbing, stern, stinging, strict,
   strident, stringent, styptic, styptic pencil, tart, tough,
   trenchant, ungentle, unsparing, vehement, violent, virulent, vise,
   vitriolic