pentagon
n. countablen. the headquarters of the United States Department of Defense. People often use this name to talk about the leaders of the American military.
n. the headquarters of the United States Department of Defense, located in Arlington, Virginia. Often used metonymically to refer to the leadership of the U.S. military establishment.
The Pentagon announced a new plan for national security.
Journalists waited outside the Pentagon for a statement regarding the recent changes in military strategy.
While the building itself is a marvel of mid-century architecture, the Pentagon is more frequently discussed in political science as the central hub of American global strategic planning.
From the shape of the building.
When referring to the U.S. military headquarters, it is a proper noun and must be capitalized and preceded by the definite article 'the'.