1. An excessively intense enthusiasm, interest, or desire; a craze: a mania for neatness.
2. Psychiatry. A manifestation of bipolar disorder, characterized by profuse and rapidly changing ideas, exaggerated sexuality, gaiety, or irritability, and decreased sleep.
3. Violent abnormal behavior. See synonyms at insanity.

[Middle English, madness, from Late Latin, from Greek maniā.]

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.