1. A psychotic or otherwise mentally ill person who exhibits violent or bizarre behavior. Not used in psychiatric diagnosis.
2. A person who has an excessive enthusiasm or desire for something: a sports maniac.
3. A person who acts in a wildly irresponsible way: maniacs on the highway.
Variant of maniacal.
[From Late Latin maniacus, maniacal, from Greek maniakos, from maniā, madness; see men-1 in the Appendix of Indo-European roots.]
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2019 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Indo-European & Semitic Roots Appendices
Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:
The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.