Compounds composed solely of an even number of carbon atoms, which form a
cage-like fused-ring
polycyclic system with twelve five-membered rings and the rest six-membered rings. The archetypal example
is [60]fullerene, where the atoms and bonds delineate a truncated icosahedron. The
term has been broadened to include any closed
cage structure consisting entirely of three-coordinate carbon atoms.
Source:
PAC, 1995, 67, 1307
(Glossary of class names of organic compounds and reactivity intermediates based on
structure (IUPAC Recommendations 1995))
on page 1336