AIR SAC - Definition

Pronunciation:		ehr sak
WordNet Dictionary

	Definition:	[n] any of the membranous air-filled extensions of the lungs of birds [n] any of the thin-walled extensions of the tracheae of insects [n] a tiny sac for holding air in the lungs; formed by the terminal dilation of tiny air passageways

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	Synonyms:	air cell, alveolus

	See Also:	bird, insect, lung, sac, sac

Webster's 1913 Dictionary

	Definition:	\Air" sac`\ (Anat.) One of the spaces in different parts of the bodies of birds, which are filled with air and connected with the air passages of the lungs; an air cell.