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