Definition of: blowhole

(blō′hōl′) noun
1. Zool. The nasal openings in the heads of certain cetaceans.
2. Geol. A small crater formed on the surface of a lava flow for the escape of gas, etc.
3. A vent for the release of gas and bad air, as from mines.
4. Metall. A defect in a metal casting due to an air bubble caught during solidification.
5. A hole in the ice to which seals, whales, etc., come to breathe.