air sac Meaning, Definition & Usage

  1. noun a tiny sac for holding air in the lungs; formed by the terminal dilation of tiny air passageways
    air cell; alveolus.
  2. noun any of the thin-walled extensions of the tracheae of insects
  3. noun any of the membranous air-filled extensions of the lungs of birds

WordNet

Air" sac`
Definitions
  1. (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.

Webster 1913