/ Dictionary / Index Z zillion: Meaning and Definition of Find definitions for: zil•lion Pronunciation: (zil'yun), [key] — n., pl. adj. -lions, -lion, —n. an extremely large, indeterminate number. —adj. of, pertaining to, or amounting to a zillion. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: zillion (Thesaurus) zillah zillionaire Related Content Daily Word Quiz: tactful Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language