Unexpected minimum or hole in a broad absorption band due to a gap being created in a broad distribution of states by
Fermi resonance.
Source:
PAC, 2021, 93, 647. 'Glossary of methods and terms used in analytical spectroscopy (IUPAC Recommendations 2019)' on page 745 (https://doi.org/10.1515/pac-2019-0203)