/ Thesaurus / A Synonyms of atomic number 57 Find synonyms for: Noun1. lanthanum, La, atomic number 57, metallic element, metalusage: a white soft metallic element that tarnishes readily; occurs in rare earth minerals and is usually classified as a rare earthWordNet 3.0 Copyright © 2006 by Princeton University. All rights reserved. Related Content Daily Word Quiz: labyrinth Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language