neptunium Meaning, Definition & Usage

  1. noun a radioactive transuranic metallic element; found in trace amounts in uranium ores; a by-product of the production of plutonium
    Np; atomic number 93.

WordNet

Nep*tu"ni*um noun
Etymology
NL.
Definitions
  1. A new metallic element, of doubtful genuineness and uncertain indentification, said to exist in certain minerals, as columbite. a radioactive element, produced in reactors from Pt or U; At. num. = 93, Sym. Np, At. Wt. 237.0482 [MW10] Hermann.

Webster 1913