trachea

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Anatomy A thin-walled, cartilaginous tube descending from the larynx to the bronchi and carrying air to the lungs.
• noun Zoology One of the internal respiratory tubes of insects and some other terrestrial arthropods, which are connected to the spiracles and are used for gas exchange.
• noun Botany A tracheary element.

from The Century Dictionary.

• noun A notable genus of noctuid moths, containing one species, T. piniperda, known to English collectors as the pinebeauty.
• noun In anatomy and zoäl.: The principal air-passage of the body; the windpipe, beginning at the larynx and ending at the bronchial tubes. In Arthropoda, as insects, one of the tubes which traverse the body and generally open by stigmata upon the exterior, thus bringing air to the blood and tissues generally, and constituting special respiratory organs.
• noun In botany, a duct or vessel; a row or chain of cells that have lost their intervening partitions and have become a single long canal or vessel.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Anat.) The windpipe. See Illust. of Lung.
• noun (Zoöl.) One of the respiratory tubes of insects and arachnids.
• noun (Bot.) One of the large cells in woody tissue which have spiral, annular, or other markings, and are connected longitudinally so as to form continuous ducts.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun anatomy A thin-walled, cartilaginous tube connecting the larynx to the bronchi; the windpipe.
• noun botany, dated xylem vessel
• noun entomology the respiratory system of insects

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun membranous tube with cartilaginous rings that conveys inhaled air from the larynx to the bronchi
• noun one of the tubules forming the respiratory system of most insects and many arachnids