/ Dictionary / Index L lutetium: Meaning and Definition of Find definitions for: lu•te•ti•um Pronunciation: (l-tē'shē-um), [key] — n. Chem. a trivalent rare-earth element. Symbol: Lu; at. wt.: 174.97; at. no.: 71. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: lutetium (Thesaurus) lutestring Luth. Related Content Daily Word Quiz: arboreal Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language