1. An absolute ruler who governs without restrictions.
2. A ruler who exercises power in a harsh, cruel manner.
3. An oppressive, harsh, arbitrary person.

[Middle English, from Old French, alteration of tyran, from Latin tyrannus, from Greek turannos.]

The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.