Adjective
antiprismatic (not comparable)
(geometry) Relating to an antiprism.
The protactinium coordination in all its tetrahalides is 8, but the arrangement is square antiprismatic in protactinium(IV) fluoride and dodecahedral in the chloride and bromide. Source: Internet
Oxygen is the most common donor atom in lanthanum complexes, which are mostly ionic and often have high coordination numbers over 6: 8 is the most characteristic, forming square antiprismatic and dodecadeltahedral structures. Source: Internet