1.NounA systematic name for an element, derived from the digits of its atomic number to which the suffix -ium is appended; normally only used for transuranic elements before or for a short period after they have been created, after which they are given a non-systematic name.
"Before IUPAC named the element with atomic number 106 “seaborgium” in honour of Glenn Seaborg, it was called by the systematic element name unnilhexium."