swelling pressure 

in colloid and surface chemistry
https://doi.org/10.1351/goldbook.S06203
That pressure difference Πsw or Π which has to be established between a gel and its equilibrium liquid, to prevent further swelling of the gel.
Source:
PAC, 1972, 31, 577. (Manual of Symbols and Terminology for Physicochemical Quantities and Units, Appendix II: Definitions, Terminology and Symbols in Colloid and Surface Chemistry) on page 615 [Terms] [Paper]