copernicium Syllabification: (copernicium)Pronunciation: /kōpərˈnisēəm/Definition of copernicium noun the chemical element of atomic number 112, a highly unstable substance that is produced artificially. (Symbol: Cn)Origin: early 21st century: from the name of Nicolaus Copernicus + -iumcopernicium in other Oxford dictionaries Definition of copernicium in the British & World English dictionary