1.NounAny of a class of allotropes of carbon having hollow molecules whose atoms lie at the vertices of a polyhedron having 12 pentagonal and 2 or more hexagonal faces.
2.NounAny closed-cage compound having twenty or more carbon atoms consisting entirely of 3-coordinate carbon atoms.
3.NounThe class of carbon allotropes consisting of tubular carbon molecules (carbon nanotubes) and spheroidal carbon molecules (traditional fullerenes).