/ Thesaurus / Q Synonyms of quintillionth Find synonyms for: Noun1. one-quintillionth, quintillionth, common fraction, simple fractionusage: one part in a quintillion equal partsAdjective1. quintillionth, ordinal (vs. cardinal)usage: the ordinal number of one quintillion in counting orderWordNet 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