delirium

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A temporary state of mental confusion and fluctuating consciousness resulting from high fever, intoxication, shock, or other causes. It is characterized by anxiety, disorientation, hallucinations, delusions, and incoherent speech.
2. n. A state of uncontrolled excitement or emotion: sports fans in delirium after their team's victory.

Century Dictionary and Cyclopedia

1. n. A disordered state, more or less temporary, of the mental faculties, occurring during illness, especially in febrile conditions. It may be the effect of inflammatory action affecting the brain, or it may be sympathetic with disease in other parts of the body, as the heart; it may be caused by long-continued and exhausting pain, or by inanition of the nervous system.
2. n. Violent excitement; exaggerated enthusiasm; mad rapture.
3. n. A hallucination or delusion; a creation of the imagination.

Wiktionary

1. n. A temporary mental state with a sudden onset, usually reversible, including symptoms of confusion, inability to concentrate, disorientation, anxiety, and sometimes hallucinations. Causes can include dehydration, drug intoxication, and severe infection.

GNU Webster's 1913

1. n. (Med.) A state in which the thoughts, expressions, and actions are wild, irregular, and incoherent; mental aberration; a roving or wandering of the mind, -- usually dependent on a fever or some other disease, and so distinguished from mania, or madness.
2. n. Strong excitement; wild enthusiasm; madness.

WordNet 3.0

1. n. a usually brief state of excitement and mental confusion often accompanied by hallucinations
2. n. state of violent mental agitation