Combination transition between the ground state and a state in which more than one vibration is excited; i.e., a transition from the ground state in which more than one quantum number increases.
Source:
PAC, 2021, 93, 647. 'Glossary of methods and terms used in analytical spectroscopy (IUPAC Recommendations 2019)' on page 764 (https://doi.org/10.1515/pac-2019-0203)