air·bag (âr?b?g?)n.1. A bag that is recessed in an automobile interior and is inflated upon impact in a crash to prevent injury to a passenger.2. An inflatable bag used for lifting heavy objects, especially one made of strong rubber used to lift vehicle or debris, as in an emergency.American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.