/ Thesaurus / A Synonyms of air sac Find synonyms for: Noun1. alveolus, air sac, air cell, sacusage: a tiny sac for holding air in the lungs; formed by the terminal dilation of tiny air passageways2. air sac, sacusage: any of the thin-walled extensions of the tracheae of insects3. air sac, sacusage: any of the membranous air-filled extensions of the lungs of birdsWordNet 3.0 Copyright © 2006 by Princeton University. All rights reserved. Related Content Daily Word Quiz: eccentric Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language