The nostril, or one of the nostrils, of whales, porpoises, and allied animals.
- Zoology A respiratory aperture, especially:
- Zoology Any of several tracheal openings in the exoskeleton of an insect or a spider.
- Zoology A small respiratory opening behind the eye of certain fishes, such as sharks, rays, and skates.
- Zoology The blowhole of a cetacean.
- An aperture or opening through which air is admitted and expelled.