Found 2 items, similar to neptunium.
English → English (WordNet) Definition: neptunium neptunium n : a radioactive transuranic metallic element; found in trace amounts in uranium ores; a by-product of the production of plutonium [syn: Np, atomic number 93]
English → English (gcide) Definition: Neptunium Neptunium \Nep*tu"ni*um\, n. [NL.] A radioactive metallic element of atomic number 93, produced in nuclear reactors from Plutonium or Uranium. Symbol Np; The atomic weight of the most stable isotope is 237.0482. [PJC]