PENTAGON /ˈpɛn.tə.ɡɑn/ ► audio Scrabble 11 Words With Friends 15 Definition noun a government building with five sides that serves as the headquarters of the United States Department of Defense. noun the United States military establishment. noun a five-sided polygon. See all 142 words you can make from PENTAGON → 8-letter words Words starting with P Words ending with N ← Unscramble different letters