What is "blowhole"

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) An air hole in a casting.

also blow-hole, 1787, of whales and porpoises, from blow (v.1) + hole.

n. 1 The spiracle, on the top of the head, through which cetaceans breathe. 2 A vent for the escape of gas. 3 A top-facing opening to a cavity in the ground very near an ocean's shore, that leads to a marine cave from which wave water and/or bursts of air are expelled. 4 An unintended cavity filled with air in a casting product. 5 A vertical opening in the top of computer cases, that let hot air, primarily from the CPU heat sink, escape quickly.

1. n. the spiracle of a cetacean located far back on the skull

2. a hole for the escape of gas or air [syn: vent, venthole, vent-hole]

In geology, a blowhole is formed as sea caves grow landwards and upwards into vertical shafts and expose themselves towards the surface, which can result in blasts of water from the top of the blowhole if the geometry of the cave and blowhole and state of the weather are appropriate.

Blowhol may refer to:

• Blowhole (anatomy), the hole at the top of a whale's or other cetacean's head
• Blowhole (geology), a hole at the inland end of a sea cave
• Blowhole Diversion Tunnel in Victoria, Australia
• A type of casting defect in metalworking
• The Blow Hole, a marine passage between Minstrel and East Cracroft Islands in the Central Coast of British Columbia, Canada

In cetology, a blowhole is the hole at the top of a Cetacean's head through which the animal breathes air. It is homologous with the nostril of other mammals. As whales reach the water surface to breathe, they will forcefully expel air through the blowhole. Not only is air expelled, but so are mucus and carbon dioxide from the animal's metabolism, which have been stored in the whale while diving. The exhalation is released into the comparably lower-pressure, colder atmosphere, and any water vapor condenses. This spray, known as the blow, is often visible from far away as a white splash, which can also be caused by water resting on top of the blowhole.

Air sacs just below the blowhole allow whales to produce sounds for communication and (for those species capable of it) echolocation. These air sacs are filled with air, which is then released again to produce sound in a similar fashion to releasing air from a balloon.

Baleen whales have two blowholes positioned in a V-shape while toothed whales have only one blowhole. The blowhole of a sperm whale, a toothed whale, is located left of centre in the frontal area of the snout, and is actually its left nostril, while the right nostril lacks an opening to the surface despite the fact that its nasal passage is otherwise well developed.

The trachea only connects to the blowhole and there is no connection to the esophagus as with humans and most other mammals. Because of this, there is no risk of food accidentally ending up in the animal's lungs, and likewise the animal cannot breathe through its mouth. As a consequence, whales have no pharyngeal reflex.