mania

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun An excessively intense enthusiasm, interest, or desire.
• noun Psychiatry A manifestation of bipolar disorder, marked usually by high energy, racing thoughts, irritability, and rapid speech.

from The Century Dictionary.

• noun Any form or phase of insanity with exaltation of spirits and rapidity of mental action; specifically, a psychoneurosis with these as the fundamental features.
• noun An eager, uncontrolled, or uncontrollable desire: as, a mania for drink; in colloquial use, a “rage” or craze for something: as, a mania for first editions.

from the GNU version of the Collaborative International Dictionary of English.

• noun Violent derangement of mind; madness; insanity. Cf. delirium.
• noun Excessive or unreasonable desire; insane passion affecting one or many people.
• noun madness from drinking; delirium tremens.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun Violent derangement of mind; madness; insanity.
• noun Excessive or unreasonable desire; insane passion affecting one or many people; fanaticism

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a mood disorder; an affective disorder in which the victim tends to respond excessively and sometimes violently
• noun an irrational but irresistible motive for a belief or action