obsessive-compulsive disorder

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

• noun A psychiatric disorder characterized by the persistent intrusion of certain repetitive, unwanted thoughts, sometimes accompanied by compulsive actions, that a person is unable to prevent and that interfere with normal functioning.

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

• noun medicine A form of anxiety characterised by an obsessive compulsion to repeatedly perform trivial or meaningless actions.

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

• noun an anxiety disorder characterized by recurrent and persistent thoughts and feelings and repetitive, ritualized behaviors