[spahy-ruh-kuhl, spir-uh-]
a breathing hole; an opening by which a confined space has communication with the outer air; air hole.
an aperture or orifice through which air or water passes in the act of respiration, as the blowhole of a cetacean.
an opening in the head of sharks and rays through which water is drawn and passed over gills.
one of the external orifices of the tracheal respiratory system of certain invertebrates, usually on the sides of the body. See diag. under insect.

1300–50; Middle English < Latin spīrāculum air hole, equivalent to spīrā(re) to breathe + -culum -cle2

spiracular [spahy-rak-yuh-ler, spi-] , adjective
prespiracular, adjective
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Based on the Random House Dictionary, © Random House, Inc. 2014.
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World English Dictionary
spiracle (ˈspaɪərəkəl, ˈspaɪrə-)
1.  any of several paired apertures in the cuticle of an insect, by which air enters and leaves the trachea
2.  a small paired rudimentary gill slit just behind the head in skates, rays, and related fishes
3.  any similar respiratory aperture, such as the blowhole in whales
4.  geology a protrusion of sediment into a lava flow, formed by the explosive transition of water into steam
[C14 (originally: breath): from Latin spīrāculum vent, from spīrāre to breathe]

Collins English Dictionary - Complete & Unabridged 10th Edition
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American Heritage
Science Dictionary
spiracle   (spĭr'ə-kəl, spī'rə-)  Pronunciation Key 
An opening through which certain animals breathe, such as the blowhole of a whale or one of the openings in the exoskeleton of an insect.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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Encyclopedia Britannica


in arthropods, the small external opening of a trachea (respiratory tube) or a book lung (breathing organ with thin folds of membrane resembling book leaves). Spiracles are usually found on certain thoracic and abdominal segments. In elasmobranch and ganoid fishes a pair of spiracles, derived from the gills, is used as a water passageway during respiration. The nasal opening of whales and other cetaceans is called a spiracle, as is the respiratory opening behind the eyes of rays and skates. In tadpoles the spiracle is the excurrent opening from the gill chamber

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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Example sentences
No spiracle, the small round hole found above the eye in lake sturgeon.
Each side of the prothorax has a spiracle, which is an opening of the respiratory system.
The spiracle is on the left side of the body and the vent is medial at the tail-body juncture.
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