·noun An air hole in a casting.
II. Blowhole ·noun A hole in the ice to which whales, seals, ·etc., come to breathe.
III. Blowhole ·noun A nostril or spiracle in the top of the head of a whale or other cetacean.
IV. Blowhole ·noun A cavern in a cliff, at the water level, opening to the air at its farther extremity, so that the waters rush in with each surge and rise in a lofty jet from the extremity.