An index of the resistance of an elastic body, such as a rock, to volume change.
• (n.) The quality of being incompressible, or incapable of reduction in volume by pressure; -- formerly supposed to be a property of liquids.
In`com·press`i·bil'i·ty noun [ Confer French incompressibilité .] The quality of being incompressible, or incapable of reduction in volume by pressure; -- formerly supposed to be a property of liquids. « The incompressibility of water is not absolute.» Rees. 
[n] - the property of being incompressible
noun the property of being incompressible