Entry 1 sense Webster, 1913 Dysprosium /dĭs-prōʹzē-əm/ · Dys·pro·si·um · IPA /dɪsˈpɹoʊ.zi.əm/ 01 n. An element of the rare earth-group. Symbol Dy; at. wt., 162.5. 1. An element of the rare earth-group. Symbol Dy; at. wt., 162.5.(Chem.)