subjacent orbital

Also contains definition of: NHOMO
https://doi.org/10.1351/goldbook.S06067
The Next-to-Highest Occupied Molecular Orbital ('NHOMO', also called 'HOMO') and the Second Lowest Unoccupied Molecular Orbital (SLUMO). Subjacent orbitals are sometimes found to play an important role in the interpretation of molecular interactions according to the @F02533@ approach.
Source:
PAC, 1994, 66, 1077. (Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994)) on page 1169 [Terms] [Paper]