ty·rant (t??r?nt) n. 1. An extremely oppressive, unjust, or cruel ruler. 2. An absolute ruler who governs without restrictions, especially one who seized power illegally. 3. An oppressive, harsh, arbitrary person: My boss is a tyrant. [Middle English, from Old French, alteration (influenced by -ant, present participle ending) of tyran, from Latin tyrannus, from Greek turannos, absolute ruler, despot, possibly from Luwian tarwanis, ruler; see ter?-2 in the Appendix of Indo-European roots.] American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.tyrant (?ta?r?nt) n1. (Government, Politics & Diplomacy) a person who governs oppressively, unjustly, and arbitrarily; despot2. any person who exercises authority in a tyrannical manner3. anything that exercises tyrannical influence4. (Historical Terms) (esp in ancient Greece) a ruler whose authority lacked the sanction of law or custom; usurper[C13: from Old French tyrant, from Latin tyrannus, from Greek turannos]Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014ty?rant (?ta? r?nt) n. 1. a sovereign or other ruler who uses power oppressively or unjustly. 2. any person in a position of authority who exercises power oppressively or despotically. 3. a tyrannical or compulsory influence. 4. an absolute ruler, esp. one in ancient Greece or Sicily. [1250?1300; Middle English