/ Thesaurus / X Synonyms of xviii Find synonyms for: Noun1. eighteen, 18, XVIII, large integerusage: the cardinal number that is the sum of seventeen and oneAdjective1. eighteen, 18, xviii, cardinal (vs. ordinal)usage: being one more than seventeenWordNet 3.0 Copyright © 2006 by Princeton University. All rights reserved. Related Content Daily Word Quiz: hedonist Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language