air sac

noun
  1. a sac containing air.
  2. alveolus(def 2).
  3. any of certain cavities in a bird's body connected with the lungs.
  4. a saclike dilation of the wall of a trachea in many insects.

Origin of air sac

First recorded in 1820–30
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

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British Dictionary definitions for air sac

air sac

noun
  1. any of the membranous air-filled extensions of the lungs of birds, which increase the efficiency of gaseous exchange in the lungs
  2. any of the thin-walled extensions of the tracheae of insects having a similar function
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

air sac in Medicine

air sac

n.
  1. A tiny, thin-walled, capillary-rich sac in the lungs where the exchange of oxygen and carbon dioxide takes place.alveolar sac
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

air sac in Science

air sac

  1. An air-filled space in the body of a bird that forms a connection between the lungs and bone cavities and aids in breathing and temperature regulation.
  2. See alveolus.
  3. A saclike enlargement in the trachea of an insect.
  4. A baglike piece of skin or tissue below the jaw of certain animals, such as the bullfrog and orangutan, that can be inflated to increase sound production.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.