Found 2 items, similar to Air sac.
English → English (WordNet) Definition: air sac air sac n 1: a tiny sac for holding air in the lungs; formed by the terminal dilation of tiny air passageways [syn: alveolus, air cell] 2: any of the thin-walled extensions of the tracheae of insects 3: any of the membranous air-filled extensions of the lungs of birds
English → English (gcide) Definition: Air sac Air sac \Air" sac`\ 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. [1913 Webster] 2. An alveolus. [PJC]