Resembling a hair; fine; minute; very slender; having minute tubes or interspaces; having very small bore; as, the capillary vessels of animals and plants.
source: Webster 1913
noun
a tube of small internal diameter; holds liquid by capillary action
source: WordNet 3.0
any of the minute blood vessels connecting arterioles with venules
source: WordNet 3.0
A tube or vessel, extremely fine or minute.
source: Webster 1913
adjective satellite
long and slender with a very small internal diameter