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.
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   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.
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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