/ Thesaurus / X Synonyms of xiii Find synonyms for: Noun1. thirteen, 13, XIII, baker's dozen, long dozen, large integerusage: the cardinal number that is the sum of twelve and oneAdjective1. thirteen, 13, xiii, cardinal (vs. ordinal)usage: being one more than twelveWordNet 3.0 Copyright © 2006 by Princeton University. All rights reserved. Related Content Daily Word Quiz: ablution Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language