superheavy element

superheavy element (plural superheavy elements)

1. (physics) an element with an extremely high atomic number; typically taken to mean beyond lawrencium (element 103, the last actinide)

There is some dispute as to how high an element's atomic number has to be before it counts as 'superheavy'; the usual criterion is anything beyond lawrencium: in other words, any transactinide.