five-sided fort; pentagonal fortification
Historical military term for a star-shaped fort with five bastions. Most famously refers to Goryōkaku in Hakodate.
The five-sided fort was designed as a star-shaped fortress.
the Pentagon (US military headquarters)
Used as a translation or nickname for the Pentagon building in the United States, based on its pentagonal shape.
The US Department of Defense is also called the Pentagon.
From 五 (five) + 稜 (ridge, angle) + 堡 (fort). A coined term for Western-style pentagonal fortifications.