n-σ* delocalization (or n-σ* no bond resonance)
Delocalization of a free electron pair (n) into an antibonding σ-orbital (σ*).
See: hyperconjugation, resonance
Source:
PAC, 1994, 66, 1077 (Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994)) on page 1146