Capillary

Webster's Dictionary of the English Language

·noun A tube or vessel, extremely fine or minute.

II. Capillary ·adj Pertaining to capillary tubes or vessels; as, capillary action.

III. Capillary ·adj Resembling a hair; fine; minute; very slender; having minute tubes or interspaces; having very small bore; as, the capillary vessels of animals and plants.

IV. Capillary ·noun A minute, thin-walled vessel; particularly one of the smallest blood vessels connecting arteries and veins, but used also for the smallest lymphatic and biliary vessels.