vein

The definition of a vein is a blood vessel that is part of the circulation system through which blood is carried or a streak of something.

(noun)

An example of a vein is what a nurse pricks with a needle when she needs to draw blood.
An example of a vein is an area in the earth where gold is found.

See vein in Webster's New World College Dictionary

noun

1. any blood vessel that carries blood from some part of the body back toward the heart
2. loosely any blood vessel
any of the riblike supports strengthening the membranous wings of an insect
any of the bundles of vascular tissue forming the framework of a leaf blade
a more or less continuous body of minerals, igneous or sedimentary rock, etc., occupying a fissure or zone, differing in nature from the enclosing rock, and usually deposited from solution by circulating water
lode (senses 1 & 2)
a streak or marking of a color or substance different from the surrounding material, as in marble or wood
1. any distinctive quality or strain regarded as running through one's character, or a speech, writing, etc.: a vein of humor in the essay
2. course or tenor of thought, feeling, action, etc.
a temporary state of mind; mood: speaking in a serious vein

Origin: ME veine < OFr < L vena

transitive verb

See vein in American Heritage Dictionary 4

noun

a. Anatomy Any of the membranous tubes that form a branching system and carry blood to the heart.
b. A blood vessel.
Botany One of the vascular bundles or ribs that form the branching framework of conducting and supporting tissues in a leaf or other expanded plant organ. Also called nervure.
Zoology One of the horny ribs that stiffen and support the wing of an insect. Also called nervure.
Geology A regularly shaped and lengthy occurrence of an ore; a lode.
A long wavy strip of a different shade or color, as in wood or marble, or as mold in cheese.
A fissure, crack, or cleft.
A pervading character or quality; a streak: “All through the interminable narrative there ran a vein of impressive earnestness” (Mark Twain). See Synonyms at streak.
a. A transient attitude or mood.
b. A particular turn of mind: spoke later in a more serious vein.