air cell

plural air cells

1. medicineA terminal dilation of the bronchiole in lungs or similar organs where gas exchange occurs.
2. medicineSpaces that contain air in the bones of the skull.
3. engineeringA prechamber in an indirect injection internal combustion engine.
4. businessAn electrochemical cell that uses air as a terminal, such as the metal-air electrochemical cell.
5. Used other than figuratively or idiomatically: see air cell.

   An air cell formed as the egg cooled and dried