/ Dictionary / Index X xi: Meaning and Definition of Find definitions for: xi Pronunciation: (zī, sī Gk. ksē), [key] — pl. xis. the 14th letter of the Greek alphabet (&Xgr;, &xgr;). the group of consonant sounds represented by this letter. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: xi (Thesaurus) Xhosa Xia Related Content Daily Word Quiz: ontiguous Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language