panic disorder

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

• noun An anxiety disorder characterized by recurrent panic attacks and sometimes resulting in the development of one or more phobias, such as agoraphobia. It may or may not be associated with a specific situational trigger.

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

• noun A anxiety disorder which consists of unpredicted severe anxiety attacks.

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

• noun an anxiety disorder characterized by unpredictable panic attacks; the attacks are usually severe but brief