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 ]
(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