in echinoderms, a system of closed tubes and ducts filled with sea water containing some protein, and functioning variously, as in locomotion, food gathering, clinging, and respiration
See water-vascular system in American Heritage Dictionary 4
(wôˈtər-văsˈkyə-lər, wŏtˈər-)
noun
A system of water-filled canals derived from the coelom that connects the tube feet of echinoderms.