'Didymium' definitions:

Definition of 'Didymium'

From: GCIDE

Didymium \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. [1913 Webster]