Neptunium

[nep'tjuːnɪəm] or [nɛp'tjunɪəm]

(noun.) a radioactive transuranic metallic element; found in trace amounts in uranium ores; a by-product of the production of plutonium.

Typist: Robinson--From WordNet

(n.) A new metallic element, of doubtful genuineness and uncertain indentification, said to exist in certain minerals, as columbite.

Editor: Timmy