Breadcrumb Home > Dictionary > Index U undecillion: Meaning and Definition of Find definitions for: un•de•cil•lion Pronunciation: (un"di-sil'yun), [key] — n., pl. adj. -lions, -lion, —n. a cardinal number represented in the U.S. by 1 followed by 36 zeros, and in Great Britain by 1 followed by 66 zeros. —adj. amounting to one undecillion in number. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. undecided undecylenic acid TrendingHere are the facts and trivia that people are buzzing about. Hanukkah Origins of the Christmas Holiday Jewish Holidays, 2010-2030 (A.M. 5770-5791) Western Christian Holidays, 2010-2030 Krampus: The Christmas Devil Kwanzaa ✖ Related Content Daily Word Quiz: anomie Analogy of the Day: Today’s Analogy Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language