The Collaborative International Dictionary of English v.0.48:

Vein \Vein\, n. [OE. veine, F. veine, L. vena.]
   1. (Anat.) One of the vessels which carry blood, either
      venous or arterial, to the heart. See Artery, 2.
      [1913 Webster]

   2. (Bot.) One of the similar branches of the framework of a
      leaf.
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   3. (Zool.) One of the ribs or nervures of the wings of
      insects. See Venation.
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   4. (Geol. or Mining) A narrow mass of rock intersecting other
      rocks, and filling inclined or vertical fissures not
      corresponding with the stratification; a lode; a dike; --
      often limited, in the language of miners, to a mineral
      vein or lode, that is, to a vein which contains useful
      minerals or ores.
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   5. A fissure, cleft, or cavity, as in the earth or other
      substance. "Down to the veins of earth." --Milton.
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            Let the glass of the prisms be free from veins.
                                                  --Sir I.
                                                  Newton.
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   6. A streak or wave of different color, appearing in wood,
      and in marble and other stones; variegation.
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   7. A train of associations, thoughts, emotions, or the like;
      a current; a course; as, reasoning in the same vein.
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            He can open a vein of true and noble thinking.
                                                  --Swift.
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   8. Peculiar temper or temperament; tendency or turn of mind;
      a particular disposition or cast of genius; humor; strain;
      quality; also, manner of speech or action; as, a rich vein
      of humor; a satirical vein. --Shak.
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            Certain discoursing wits which are of the same
            veins.                                --Bacon.
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            Invoke the Muses, and improve my vein. --Waller.
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The Collaborative International Dictionary of English v.0.48:

Vein \Vein\, v. t. [imp. & p. p. Veined; p. pr. & vb. n.
   Veining.]
   To form or mark with veins; to fill or cover with veins.
   --Tennyson.
   [1913 Webster]

WordNet (r) 3.0 (2006):

vein
    n 1: a blood vessel that carries blood from the capillaries
         toward the heart; "all veins except the pulmonary vein
         carry unaerated blood" [syn: vein, vena, venous blood
         vessel]
    2: a distinctive style or manner; "he continued in this vein for
       several minutes"
    3: any of the vascular bundles or ribs that form the branching
       framework of conducting and supporting tissues in a leaf or
       other plant organ [syn: vein, nervure]
    4: a layer of ore between layers of rock [syn: vein, mineral
       vein]
    5: one of the horny ribs that stiffen and support the wing of an
       insect [syn: vein, nervure]
    v 1: make a veinlike pattern

Moby Thesaurus II by Grady Ward, 1.0:

197 Moby Thesaurus words for "vein":
   affectation, aorta, arteriole, artery, attitude, band, bar, bed,
   bespangle, bespeckle, bespot, blood vessel, blotch, body-build,
   bonanza, brand, capillary, carotid, cast, character,
   characteristic, characteristics, check, checker, chimney, chute,
   command of language, complexion, composition, constituents,
   constitution, cornucopia, country rock, course, crasis, cue,
   dapple, deposit, dharma, diathesis, dike, disposition, dot, ethos,
   exaggeration, expression of ideas, fashion, feeling,
   feeling for words, fettle, fiber, flake, fleck, font,
   form of speech, fount, fountain, frame, frame of mind, freckle,
   gangue, genius, gold mine, grace of expression, grain,
   grandiloquence, gruel, habit, harlequin, heart, hint, hue, humor,
   humors, ilk, inflation, iris, jugular vein, kind, lath, line,
   literary style, lode, lodestuff, maculate, makeup, manner,
   manner of speaking, mannerism, marble, marbleize, matrix,
   mere shadow, mind, mine, mineral deposit, mode, mode of expression,
   mold, mood, morale, motley, mottle, nature, note, ore bed, paper,
   pattern, pay dirt, peculiarity, pepper, personal style, physique,
   polychrome, polychromize, portal vein, property, pulmonary artery,
   pulmonary vein, quality, quarry, rail, rainbow, rake, resource,
   rhetoric, seam, sense of language, shade, shadow, shaving, shoot,
   skeleton, slat, slip, somatotype, sort, soup, source,
   source of supply, spangle, speck, speckle, spirit, spirits,
   splinter, splotch, spot, spring, sprinkle, stamp, staple,
   state of mind, stigmatize, stipple, stock, strain, stratum, streak,
   stria, striate, striation, stripe, stud, style, stylistic analysis,
   stylistics, suchness, suggestion, suspicion, system, tattoo,
   temper, temperament, tendency, tenor, tessellate, the grand style,
   the plain style, the sublime, thread, tincture, tinge, tone, touch,
   trace, trick, type, variegate, veinlet, vena cava, venation,
   venule, wafer, way, well, wellspring