/ Thesaurus / A Synonyms of atomic number 99 Find synonyms for: Noun1. einsteinium, Es, E, atomic number 99, metallic element, metalusage: a radioactive transuranic element produced by bombarding plutonium with neutronsWordNet 3.0 Copyright © 2006 by Princeton University. All rights reserved. Related Content Daily Word Quiz: denizen Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language