khan:The specific title (usually with great, †grand, or the additions of Tartary, of Cathay) given to the successors of Chingīz Khan, who were supreme rulers over the Turkish, Tartar, and Mongol tribes, as well as emperors of China, during the middle ages.——Oxford English Dictionary

khan:a ruler or official in India or central Asia, or their title.——Longman Dictionary of Contemporary English  @en