Webster’s Revised Unabridged Dictionary · 1913
Decipium
De·cip′i·um (dē·sĭp′ĭ·ŭm), n. [NL., fr. L. decipere to deceive.] (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.