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WordNet
accessory hemiazygos vein

n. a vein formed by the union of the 4th to 7th posterior intercostal veins; empties into the azygos vein [syn: accessory hemiazygous vein, vena hemiazygos accessoria]

Wikipedia
Accessory hemiazygos vein

The accessory hemiazygos vein is a vein on the left side of the vertebral column that generally drains the fifth through eighth intercostal spaces on the left side of the body.