pentagon

noun

1. a polygon having five angles and five sides.
2. the Pentagon,
   1. a building in Arlington, Virginia, having a plan in the form of a regular pentagon, containing most U.S. Defense Department offices.
   2. the U.S. Department of Defense; the U.S. military establishment.

noun

1. a polygon having five sides

noun

1. the five-sided building in Arlington, Virginia, that houses the headquarters of the US Department of Defense
2. the military leadership of the US

n.plane figure with five angles and five sides, 1560s, from Middle French pentagone or directly from Late Latin pentagonum “pentagon,” from Greek pentagonon, noun use of neuter of adjective pentagonos “five-angled,” from pente “five” (see five) + gonia “angle” (see knee (n.)). The U.S. military headquarters Pentagon was completed 1942, so called for its shape; used allusively for “U.S. military leadership” from 1945. Related: Pentagonal. In nature, pentagonal symmetry is rare in inanimate forms. Packed soap bubbles seem to strive for it but never quite succeed, and there are no mineral crystals with true pentagonal structures. But pentagonal geometry is basic to many living things, from roses and forget-me-nots to sea urchins and starfish. [Robert Bringhurst, “The Elements of Typographic Style,” 1992]

1. A polygon having five sides.

An immense five-sided building in Virginia, just outside Washington, D.C., that serves as headquarters for the Department of Defense. A polygon having five sides.