vein / vān/ • n. 1. any of the tubes forming part of the blood circulation system of the body, carrying in most cases oxygen-depleted blood toward the heart. Compare with artery. ∎  (in general and figurative use) a blood vessel: he felt the adrenaline course through his veins. ∎  (in plants) a slender rib running through a leaf or bract, typically dividing or branching, and containing a vascular bundle. ∎  (in insects) a hardened branching rib that forms part of the supporting framework of a wing, consisting of an extension of the tracheal system; a nervure. ∎  a streak or stripe of a different color in wood, marble, cheese, etc. ∎  a fracture in rock containing a deposit of minerals or ore and typically having an extensive course underground. ∎  subsurface water, esp. as considered a source or potential source of water for a well or wells and thought of as flowing in a channel. ∎ fig. a source of a specified quality or other abstract resource: he managed to tap into the thick vein of discontent to his own advantage. 2. [in sing.] a distinctive quality, style, or tendency: he closes his article in a somewhat humorous vein.DERIVATIVES: vein·less adj.vein·let / -lit/ n.vein·like / -ˌlīk/ adj. & adv.vein·y adj. (vein·i·er , vein·i·est ) .

vein
1. A blood vessel that carries blood towards the heart. Most veins carry deoxygenated blood (the pulmonary vein is an exception). The largest veins are fed by smaller ones, which are formed by the merger of venules. Veins have thin walls and a relatively large internal diameter. Valves within the veins ensure that the flow of blood is always towards the heart. Compare artery.

2. A vascular bundle in a leaf (see venation).

3. Any of the tubes of chitin that strengthen an insect's wing.

vein In mammals, vessel that carries deoxygenated blood to the heart. An exception is the pulmonary vein, which carries oxygenated blood from the lungs to the left upper chamber of the heart. See also artery; vena cava

vein
A. tubular vessel in which blood is conveyed through the animal body XIII (of a leaf XVI);

B. †small channel through which water flows XIII; line of deposit of mineral or earthy matter XIV;

C. strain of some quality; characteristic style; personal disposition; mood XVI. — (O)F. veine :- L. vēna.
Hence veiny (-Y1) XVI.

vein (vayn) n. a blood vessel conveying blood towards the heart. All veins except the pulmonary vein carry deoxygenated blood from the tissues to the vena cava. Veins contain valves that assist the flow of blood back to the heart. (See illustrations.) Anatomical name: vena.
—venous (vee-nŭs) adj.