davyum

from The Century Dictionary.

• noun A metal of the platinum group, whose discovery was announced in 1877 by Kern of St. Petersburg.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Chem.) A rare metallic element found in platinum ore. It is a white malleable substance. Symbol Da. Atomic weight 154.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A supposed chemical element discovered in 1877, later found to be a mixture of iridium and rhodium.