neurosis

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

• noun A psychological state characterized by excessive anxiety or insecurity, compensated for by various defense mechanisms and lacking evidence of neurologic or other organic disease. No longer used in psychiatric diagnosis.

from The Century Dictionary.

• noun A nervous disease without recognizable anatomical lesion, as epilepsy, hysteria, neuralgia, etc.
• noun In neurology, a process of nervous excitation: used thus generally only in opposition to psychosis, a mental process.

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

• noun (Med.) A functional nervous affection or disease, that is, a disease of the nerves without any appreciable change of nerve structure.
• noun (Psychiatry) a mental or emotional disorder that affects only part of the personality, and involves less distorted perceptions of reality than a psychosis. As used in medicine, anxiety is a prominent characteristic, and the condition may be accompanied by psychosomatic symptoms. Phobias and compulsive behavior are common varieties.

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

• noun pathology A mental disorder, less severe than psychosis, marked by anxiety or fear

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

• noun a mental or personality disturbance not attributable to any known neurological or organic dysfunction