/ Dictionary / Index O octillion: Meaning and Definition of Find definitions for: oc•til•lion Pronunciation: (ok-til'yun), [key] — n., pl. adj. -lions, -lion, —n. a cardinal number represented in the U.S. by 1 followed by 27 zeros, and in Great Britain by 1 followed by 48 zeros. —adj. amounting to one octillion in number. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: octillion (Thesaurus) octet octo- Related Content Daily Word Quiz: acquiesce Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language