The government in the Ottoman Empire is best described as

sultanate

Explanation:

The Ottoman Empire, ever since its formation and until its later phases of existence has had a sultan as its leader. The empire was officially a sultanate. The sultan was the person that had absolute power in the empire, and there was no authority that can control and regulate his actions. What the sultan wanted, the subjugated performed. The sultanate only finished when Mustafa Kemal Ataturk led a revolution and managed to take over the government, thus abolishing the sultanate and trying to create a modern nations.