The term 'Royal Russian, Once' can be summarized by the crossword solution 'TSAR, ' which is a four-letter word. TSAR was the title of the monarchs of Russia from 1547 to 1917. The term is derived from the Latin word 'CAESAR, ' which was used to refer to Roman emperors. Tsars were absolute rulers and held immense power over their subjects. They were also known as autocrats and were responsible for the expansion of the Russian Empire.