A localized valence bond representation of a molecule. This describes pictorially an electronic wavefunction that makes some contribution to the state wavefunction of the system. resonance hybrids are needed to describe the state of a system when that system is not adequately described by a single Lewis structure.
PAC, 1999, 71, 1919. 'Glossary of terms used in theoretical organic chemistry' on page 1961 (https://doi.org/10.1351/pac199971101919)