  Isothermal compressibility ($\kappa_{\rm T}$) is an important thermodynamic
observable which gives information about the deviation of a system from perfect
fluid behavior. In this work, for the first time we have estimated the
isothermal compressibility of QCD matter formed in high energy hadronic and
nuclear collisions using color string percolation model (CSPM), where we
investigate the change in $\kappa_{\rm T}$ as a function of final state charged
particle multiplicity and initial percolation temperature across various
collision species. The estimated initial percolation temperature for different
collision systems at different collision energies helps us to have a better
understanding of the system at the initial phase of evolution. The comparison
of the CSPM results for isothermal compressibility with that for the well known
fluids, indicates that the matter formed in heavy-ion collisions might be the
{\it closest perfect fluid} found in nature. This estimation complements the
well-known observation of minimum shear viscosity to entropy density ratio for
a possible QGP medium created in heavy-ion collision experiments. A threshold
of pseudorapidity density of charged particles, $\langle dN_{\rm ch}/d\eta
\rangle \geq 20 $ in the final state event multiplicity is observed, after
which one may look for a possible QGP formation at the LHC energies.
