The term originally applied to compounds having two p-phenylene groups held face to face by –[CH2]n bridges. It now designates compounds having (i) mancude-ring systems, or assemblies of mancude-ring systems, and (ii) atoms and/or saturated or unsaturated chains as alternate components of a large ring. E.g. [2.2](1,4)(1,4)cyclophane [or 1(1,4),4(1,4)-dibenzenacyclohexaphane].
Many chemists include in this class any bridged aromatic system, irrespective of the attachment positions of the bridge.
PAC, 1995, 67, 1307 (Glossary of class names of organic compounds and reactivity intermediates based on structure (IUPAC Recommendations 1995)) on page 1330