a soft, silvery-white chemical element, one of the rare-earth elements and the last member of the lanthanide series: symbol, Lu; at. no., 71
See lutetium in American Heritage Dictionary 4
also lu·te·ci·um(lo͞o-tēˈshē-əm)
noun Symbol Lu
A silvery-white rare-earth element that is exceptionally difficult to separate from the other rare-earth elements, used in nuclear technology. Atomic number 71; atomic weight 174.97; melting point 1,663°C; boiling point 3,395°C; specific gravity 9.840 (at 25°C); valence 3. See Table at element.