/ Thesaurus / L Synonyms of lanthanon Find synonyms for: Noun1. rare earth, rare-earth element, lanthanoid, lanthanide, lanthanon, group, groupingusage: any element of the lanthanide series (atomic numbers 57 through 71)WordNet 3.0 Copyright © 2006 by Princeton University. All rights reserved. Related Content Daily Word Quiz: tenacious Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language