n. [ NL. Dee Neo-, and Didymium. ] (Chem.) The chemical element of atomic number 60, one of the rare earth elements. Symbol Nd. Atomic weight 144.27. It is a rare metallic element occurring in combination with cerium, lanthanum, and other rare metals, and forming amethyst-colored salts. It was originally thought to be part of a supposed new element didymium, obtained from cerite in 1843. Later this was resolved into two elements, neodymium and praesodymium by von Welsbach in 1885. It is chiefly trivalent. It is a faintly yellow metal. [ 1913 Webster +PJC ]