noun an air hole in a casting.
2. blowhole ·noun a hole in the ice to which whales, seals, ·etc., come to breathe.
3. blowhole ·noun a nostril or spiracle in the top of the head of a whale or other cetacean.
4. 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.