Definitions
1.NounA terminal dilation of the bronchiole in lungs or similar organs where gas exchange occurs.
2.NounSpaces that contain air in the bones of the skull.
3.NounA prechamber in an indirect injection internal combustion engine.
4.NounAn electrochemical cell that uses air as a terminal, such as the metal-air electrochemical cell.
5.NounUsed other than figuratively or idiomatically: see air cell."An air cell formed as the egg cooled and dried"