air sac, n.
any of the membranous air-filled extensions of the lungs of birds
<noun.animal>
air sac
any of the thin-walled extensions of the tracheae of insects
<noun.animal>
air sac
a tiny sac for holding air in the lungs; formed by the terminal dilation of tiny air passageways
<noun.body> freq. cnt.: 5 freq. cnt.: 5
air cell air sac alveolus