di·dym·i·um 
(dī-dĭmē-əm)
(dī-dĭmē-əm)n.
1. A metallic mixture, once considered an element, composed of neodymium and praseodymium.
2. A mixture of rare-earth elements and their oxides used chiefly in manufacturing and in coloring various forms of glass.
[From Greek didumos, twin, double (from the fact that it was usually found associated with the previously discovered lanthanum); see dwo- in the Appendix of Indo-European roots.]
- offsides
- offsite
- off (someone's) back
- off someone's back
- off (someone's) case
- off someone's case
- off-speed
- offspring
- offstage
- off-the-books
- off the cuff
- off-the-cuff
- off the grid
- off-the-grid
- off the ground
- off the hook
- off-the-rack
- off the rack
- off-the-record
- off the record
- off-the-shelf
- off the shelf
- off the top of head
- off the top of (one's) head
- off the top of one's head