/ Dictionary / Index P pentagon: Meaning and Definition of Find definitions for: pen•ta•gon Pronunciation: (pen'tu-gon"), [key] — n. a polygon having five angles and five sides. a building in Arlington, Virginia, having a plan in the form of a regular pentagon, containing most U.S. Defense Department offices. the U.S. Department of Defense; the U.S. military establishment. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: pentagon (Thesaurus) pentaerythritol tetranitrate pentagonal dodecahedron Related Content Daily Word Quiz: philanthropy Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language