Vein

n. blood vessel which carries blood to the heart; any blood vessel (Informal); bundle of sap-carrying vessels in plants; band of ore between rock layers; pervading quality, mood; vessels in insect wings

In the circulatory system, a vein is a blood vessel that carries blood toward the heart. The majority of veins in the body carry low-oxygen blood from the tissues back to the heart; the exceptions being the pulmonary and umbilical veins which both carry oxygenated blood.
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Vein a vessel in which blood flows toward the heart, in the systemic circulation carrying blood that has given up most of its oxygen. [more]Vein - Community and Resources

Noun
1. a blood vessel that carries blood from the capillaries toward the heart; all veins except the pulmonary carry unaerated blood
(synonym) vena, venous blood vessel
(hypernym) blood vessel
(hyponym) accessory cephalic vein, vena cephalica accessoria
(part-holonym) circulatory system, cardiovascular system
2. a distinctive style or manner; "he continued in this vein for several minutes"
(hypernym) expressive style, style
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
(synonym) nervure
(hypernym) vascular bundle, vascular strand, fibrovascular bundle
(hyponym) midrib, midvein
4. a layer of ore between layers of rock
(synonym) mineral vein
(hypernym) geological formation, formation
(hyponym) bonanza
5. one of the horny ribs that stiffen and support the wing of an insect
(synonym) nervure
(hypernym) rib
Verb
1. make a veinlike pattern
(hypernym) stain

(v. t.)
To form or mark with veins; to fill or cover with veins.
  

(n.)
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.
  

(n.)
One of the vessels which carry blood, either venous or arterial, to the heart. See Artery, 2.
  

(n.)
One of the similar branches of the framework of a leaf.
  

(n.)
One of the ribs or nervures of the wings of insects. See Venation.
  

(n.)
A train of association, thoughts, emotions, or the like; a current; a course.
  

(n.)
A streak or wave of different color, appearing in wood, and in marble and other stones; variegation.
  

(n.)
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.
  

(n.)
A fissure, cleft, or cavity, as in the earth or other substance.