Di*dym"i*um (?), n. [NL., fr. Gr. twin.] Chem.
A rare metallic substance usually associated with the metal cerium; -- hence its name. It was formerly supposed to be an element, but has since been found to consist of two simpler elementary substances, neodymium and praseodymium. See Neodymium, and Praseodymium.
© Webster 1913.