An idealized condition in which compressibility vanishes. Most liquids are nearly incompressible. For shallow layers of the atmosphere with velocity fluctuations much less than the speed of sound, incompressibility is a good approximation and is often made for mathematical convenience. For a fluid with a density depending on temperature, incompressibility does not imply non- divergence. See anelastic approximation, Boussinesq approximation.

The quality of being incompressible, or incapable of reduction in volume by pressure; -- formerly supposed to be a property of liquids.

An index of the resistance of an elastic body, such as a rock, to volume change.

the property of being incompressible