/ Thesaurus / U Synonyms of uranium 238 Find synonyms for: Noun1. uranium 238, uranium, U, atomic number 92usage: the commonest isotope of uranium; it is not fissionable but when irradiated with neutrons it produces fissionable plutonium 239WordNet 3.0 Copyright © 2006 by Princeton University. All rights reserved. Related Content Daily Word Quiz: inutiae Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language