/ Dictionary / Index R rare earth: Meaning and Definition of Find definitions for: rare' earth' Pronunciation: [key] — Chem. Chem. the oxide of any of the rare-earth elements contained in various minerals. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. rare book rare-earth element Related Content Daily Word Quiz: vertigo Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language