Noun has 3 senses

• air sac(n = noun.body) air cell, alveolus - a tiny sac for holding air in the lungs; formed by the terminal dilation of tiny air passageways;



• air sac(n = noun.animal) - any of the thin-walled extensions of the tracheae of insects;



• air sac(n = noun.animal) - any of the membranous air-filled extensions of the lungs of birds;