accidental degeneracy 

https://doi.org/10.1351/goldbook.08221
Condition that occurs when two or more normal transitions have the same energy as a matter of coincidence, as opposed to because of symmetry conditions.
Source:
PAC, 2021, 93, 647. (Glossary of methods and terms used in analytical spectroscopy (IUPAC Recommendations 2019)) on page 651 [Terms] [Paper]