pentagon

noun

1. A polygon with five sides and five angles.

   “Imagine a vast sheet of paper on which straight Lines, Triangles, Squares, Pentagons, Hexagons, and other figures, instead of remaining fixed in their places, move freely about, […]”

2. A fort with five bastions.

name

1. The headquarters of the United States Department of Defense.
2. (metonymically)The United States Department of Defense.

   “The Vietnamese people inspired youth of all nationalities […] by demonstrating that the determination of a people to fight for their sovereignty and right to self-determination was an unconquerable force, even in the face of Pentagon might.”

   “Asked by CNN what measures DHS was taking after the Pentagon leaks, Mayorkas said the department issued a reminder to employees and that he had directed a review.”