/ Thesaurus / A Synonyms of atomic number 61 Find synonyms for: Noun1. promethium, Pm, atomic number 61, metallic element, metalusage: a soft silvery metallic element of the rare earth group having no stable isotope; was discovered in radioactive form as a fission product of uraniumWordNet 3.0 Copyright © 2006 by Princeton University. All rights reserved. Related Content Daily Word Quiz: loathe Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language