capillary

Concise Oxford English Dictionary © 2008 Oxford University Press:
capillary /kəˈpɪləri/

▶noun (pl. capillaries)

• 1 Anatomy any of the fine branching blood vessels that form a network between the arterioles and venules.

• 2 (also capillary tube) a tube with an internal diameter of hair-like thinness.

▶adjective relating to capillaries or capillarity.

– origin C17: from L. capillaris, from capillus ‘hair’, influenced by OFr. capillaire.