/ Dictionary / Index U undecagon: Meaning and Definition of Find definitions for: un•dec•a•gon Pronunciation: (un-dek'u-gon"), [key] — n. a polygon having 11 angles and 11 sides. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: undecagon (Thesaurus) undaunted undeceive Related Content Daily Word Quiz: endear Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language