excluded volume of a macromolecule

in polymers
The volume from which a macromolecule in a dilute solution of a macromolecule effectively excludes all other macromolecules. The excluded volume of a macromolecule depends on the Gibbs and Helmholtz energies of mixing of solvent and polymer, i.e. on the thermodynamic quality of the solvent, and is not a measure of the geometrical volume of that macromolecule.
Purple Book, 1st ed., p. 58 (http://old.iupac.org/publications/books/author/metanomski.html)