When a sol is colloidally unstable (i.e. the rate of aggregation is not negligible) the formation of aggregates is called coagulation or flocculation.
Orange Book, 2nd ed., p. 85 (http://media.iupac.org/publications/analytical_compendium/)
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 609 (https://doi.org/10.1351/pac197231040577)