long and narrow strip of water made for boats or for irrigation | a wide channel containing blood; does not have the coating of an ordinary blood vessel |
a bodily passage or tube lined with epithelial cells and conveying a secretion or other substance | any of various air-filled cavities especially in the bones of the skull |
(astronomy) an indistinct surface feature of Mars once thought to be a system of channels; they are now believed to be an optical illusion | an abnormal passage leading from a suppurating cavity to the body surface |