Agoraphobia: An abnormal and persistent fear of public places or open areas, especially those from which escape could be difficult or in which help might not be immediately accessible. Persons with agoraphobia frequently also have panic disorder. People with mild agoraphobia often live normal lives by avoiding anxiety-provoking situations. In the most severe agoraphobia, the victims may be incapacitated and homebound. Agoraphobia tends to start in the mid to late20s, and the onset may appear to be triggered by a traumatic event.