Car safety device (3,3)
(Other definitions for air bag that I've seen before include "Balloon or protective device in car" , "Car safety cushion" , "A safety feature in a car" , "A safety restraint in a car" , "Safety device in a motor car" .)
(Other definitions for airbag that I've seen before include "thing rarely subject to inflation" , "Rapidly-inflating car safety device" , "cushion" , "that's deployed to save a life" , "safety feature" .)