The term 'BYGONE TYRANT' can be broken down into two words: 'BYGONE' and 'TYRANT'. The word 'BYGONE' means something that is no longer in existence, while the word 'TYRANT' refers to a cruel and oppressive ruler. The crossword solution for this term is 'TSAR', which is a title used by rulers of Russia from 1547 to 1917. Tsars were absolute monarchs who had complete control over their subjects and were known for their oppressive rule.