capillary

(noun) a tube of small internal diameter; holds liquid by capillary action. Synonyms: capillary tube, capillary tubing.

(noun) any of the minute blood vessels connecting arterioles with venules. Synonyms: capillary vessel.

(adj) of or relating to hair.

(adj) long and slender with a very small internal diameter. Synonyms: hairlike. Example: "A capillary tube."