/ Dictionary / Index Y yttrium: Meaning and Definition of Find definitions for: yt•tri•um Pronunciation: (i'trē-um), [key] — n. Chem. a rare trivalent metallic element, found in gadolinite and other minerals. Symbol: Y; at. wt.: 88.905; at. no.: 39; sp. gr.: 4.47. Cf. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: yttrium (Thesaurus) yttriferous yttrium metal Related Content Daily Word Quiz: quandary Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language