- [countable] (
geometry 幾何 a flat shape with five straight sides and five angles 五邊形；五角形 
- the Pentagon[singular]
the building near Washington DC that is the headquarters of the US Department of Defense and the military leaders 五角大樓（指美國國防部） a spokesman for the Pentagon 美國國防部發言人
Word Originlate 16th cent.: via Latin from Greek pentagōnon, neuter (used as a noun) of pentagōnos ‘five-angled’.