blowhole

Blow"hole`, n. 1. 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. 2. A nostril or spiracle in the top of the head of a whale or other cetacean. Note: There are two spiracles or blowholes in the common whales, but only one in sperm whales, porpoises, etc. 3. A hole in the ice to which whales, seals, etc., come to breathe. 4. (Founding) Defn: An air hole in a casting.

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