noun. A respiratory aperture, especially.

noun. Any of several tracheal openings in the exoskeleton of an insect, spider, or other terrestrial arthropod.

noun. A small respiratory opening behind the eye of most sharks and rays and certain other fishes.

noun. The blowhole of a cetacean.

noun. An aperture or opening through which air is admitted and expelled.

noun. A vent for small explosive outbreaks, produced upon the surface of a still highly heated and at least partially molten lava-stream by the escape of imprisoned vapors. A little cone of ejected clots may gather around it.

noun. An aperture or orifice.

noun. In zoology, an aperture, orifice, or vent through which air, vapor, or water passes in the act of respiration; a breathing-hole; a spiraculum: applied to many different formations.

noun. The nostril, or one of the nostrils, of whales, porpoises, and allied animals.

noun. undefined

noun. One of the external openings communicating with the air tubes or tracheæ of insects, myriapods, and arachnids. They are variable in number, and are usually situated on the sides of the thorax and abdomen, a pair to a segment. These openings are usually elliptical, and capable of being closed. See Illust. under Coleoptera.

noun. A tubular orifice communicating with the gill cavity of certain ganoid and all elasmobranch fishes. It is the modified first gill cleft.

noun. Any small aperture or vent for air or other fluid.

noun. A pore or opening used (especially by spiders and some fish) for breathing.

noun. The blowhole of a whale.

noun. Any small aperture or vent for air or other fluid.

noun. a breathing orifice