The removal of a degeneracy of atomic or molecular levels in a molecule or ion with a given symmetry, induced by the attachment or removal of ligands to produce reduced symmetries.
See: crystal field splitting
Source:
PAC, 1996, 68, 2223. 'Glossary of terms used in photochemistry (IUPAC Recommendations 1996)' on page 2251 (https://doi.org/10.1351/pac199668122223)