means A ruler who holds absolute power and wields it cruelly, oppressively, and without accountability.

from From Greek 'tyrannos,' a word that originally carried no insult — it simply meant an absolute ruler who seized power outside the usual hereditary line, sometimes even a popular one. The Greeks borrowed the term from an older non-Greek language, possibly Lydian, so its deepest roots are murky. It passed through Latin 'tyrannus' and Old French 'tyrant' into English, picking up its dark moral stain along the way as such rulers earned their reputations the hard way.