†(a) elasticity of the air (obsolete); (b) Mechanics a damping device that uses compressed air, as in pneumatic suspension systems.

The power to spring back into shape or position after compression, bending, etc.; the quality of… With reference to the resistance to compression…

esp. in Physics and Aeronautics. The quality in virtue of which the volume of a gas, etc., may be diminished without decrease of its mass.