decipium

from The Century Dictionary.

• noun Chemical symbol, Dp; atomic weight, 106 if the oxid is DpO, or 171 if, as is likely, the oxid is Dp₂O₃.

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

• noun (Chem.) A supposed rare element, said to be associated with cerium, yttrium, etc., in the mineral samarskite, and more recently called samarium. Symbol Dp. See samarium.

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

• noun obsolete Proposed name for a chemical element isolated from samarskite, later found to be a mixture of samarium and other rare earth elements.