/ Dictionary / Index Q quadrillion: Meaning and Definition of Find definitions for: quad•ril•lion Pronunciation: (kwo-dril'yun), [key] — n., pl. adj. -lions, -lion, —n. a cardinal number represented in the U.S. by 1 followed by 15 zeros, and in Great Britain by 1 followed by 24 zeros. —adj. amounting to one quadrillion in number. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: quadrillion (Thesaurus) quadrille quadrinomial Related Content Daily Word Quiz: reticent Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language