1. (noun)canal (astronomy) an indistinct surface feature of Mars once thought to be a system of channels; they are now believed to be an optical illusion
2. (noun)duct, epithelial duct, canal, channel a bodily passage or tube lined with epithelial cells and conveying a secretion or other substance
"the tear duct was obstructed"; "the alimentary canal"; "poison is released through a channel in the snake's fangs"
3. (noun)canal long and narrow strip of water made for boats or for irrigation
4. (verb)canal, canalize, canalise provide (a city) with a canal