The matter which density is not dependent on pressure :

\rho(p, T) = \rho_0(T) = {\rm const}

which is equivalent to zero compressibility:

 c(T, p) \equiv 0 \Leftrightarrow  \frac{d \rho}{ dp} = 0

where

Temperature

Incompressible matter does not exist but in many practical applications the pressure variation may stay within the sufficiently narrow range where a given matter can be considered as incompressible.

See also