What does the term "Sublime Porte" refer to?

The "Sublime Porte", was a term, along with Ottoman Porte and High Porte, used to refer to the Ottoman Empire's central government. The origin of the expression comes from the practice of Eastern rulers would announce judgments or decisions at the gate of the palace. It was a typical practice done during the Byzantine Empire and was adopted by the successor rulers of the Byzantines, the Ottomans. Before Constantinople fell to the Ottomans, their palace in Bursa or the gate leading to the palace became known as the "High Gate". After the conquest of Constantinople, the gate known as the Imperial Gate was termed the "High Gate" or "Sublime Porte".

Use of the term in the West dates back to the alliance between Suleiman the Magnificent and King Francis I of France which was completed in 1536, French diplomats walked through the gate known as the "Bab-ı Ali" in order to reach the seat of government, referring to the gate as the "Sublime Porte". Other European languages adopted the term to refer not only to the gate but as a term for the Ottoman Empire's government.

"Sublime Porte" can be considered a "synecdoche", a word or phrase that is a figure of speech that denotes one thing that is related to that thing. An example is a structure or building that refers to the occupants. For example, "Number 10" refers to the United Kingdom of Great Britain's Office of the Prime Minister, "The Pentagon" refers to the U.S. Department of Defense.