say it: PEN-ti-gahn
pentagon is a noun meaning "a government building with five sides that serves as the headquarters of the United States Department of Defense". It carries 3 recorded senses.
a government building with five sides that serves as the headquarters of the United States Department of Defense
a five-sided polygon
Forms marked · are formed by the regular rule rather than recorded in the source data. English keeps a few hundred irregulars and the rest follow the pattern, so the rule is right far more often than not — but it is a rule, and the mark says so.
Definitions, synonyms and semantic relations for pentagon come from Princeton University’s WordNet. The pronunciation comes from the CMU Pronouncing Dictionary. Commonness is measured against a corpus of everyday English. Full sources and licences.