Essentially synonymous with @R05326@. The term is particularly associated with the picture of π-electrons as less localized in an actual molecule than in a @L03513@. The term is intended to imply that the correct representation of a structure is intermediate between two or more Lewis formulae.
See also:
aromatic (Def. 2)
PAC, 1994, 66, 1077. (Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994)) on page 1139 [Terms] [Paper]