/ Dictionary / Index J jillion: Meaning and Definition of Find definitions for: jil•lion Pronunciation: ( jil'yun), [key] — Informal. Informal. —n. an indefinitely vast number; zillion. —adj. of or noting such a quantity: a jillion problems. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: jillion (Thesaurus) jillet Jilolo Related Content Daily Word Quiz: secular Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language