closo-

https://doi.org/10.1351/goldbook.C01106
An affix used in names to denote a @[email protected] or closed structure, especially a boron skeleton that is a polyhedron having all triangular faces.
Sources:
Blue Book, p. 464 [Terms] [Book]
PAC, 1972, 30, 681. (Nomenclature of Inorganic Boron Compounds) on page 686 [Terms] [Paper]
Red Book, 3rd ed., p. 245 [Terms] [Book]