syrinx

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

• noun Zoology The vocal organ of a bird, consisting of thin vibrating muscles at or close to the division of the trachea into the bronchi.

from The Century Dictionary.

• Same as Pan's pipes (which see, under pipe).
• In Egypt. archæol., a narrow and deep rock-cut channel or tunnel forming a characteristic feature of Egyptian tombs of the New Empire.
• In anatomy, the Eustachian tube.
• In ornithology, the voice-organ of birds; the lower larynx, situated at or near the bifurcation of the trachea into the bronchi, and serving to modulate the voice, as in singing.
• In surgery, a fistula.
• noun In some of the brachiopods, like Syringothyris, a split tubular structure developed from the deltidial plates, lying within the umbonal region of the ventral valve, and inclosing or forming a passage for the pedicle.

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

• noun (Mus.) A wind instrument made of reeds tied together; -- called also pandean pipes.
• noun (Anat.) The lower larynx in birds.

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

• noun A set of pan-pipes.
• noun A narrow channel cut in rock, especially in ancient Egyptian tombs.
• noun zoology The voice organ in birds.
• noun medicine A rare, fluid-filled neuroglial cavity within the spinal cord or in the brain stem

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

• noun the vocal organ of a bird
• noun a primitive wind instrument consisting of several parallel pipes bound together