The American Heritage® Dictionary of the English Language, 4th Edition
n. A persistent, abnormal, and irrational fear of a specific thing or situation that compels one to avoid it, despite the awareness and reassurance that it is not dangerous.
n. An irrational or obsessive fear or anxiety, usually of or about something particular.
The Century Dictionary and Cyclopedia
n. Any morbid uncontrollable dread or fear.
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
n. an anxiety disorder characterized by extreme and irrational fear of simple things or social situations
Word Usage
"If the patient does not recognize the fear as excessive or unreasonable, it becomes very difficult to actually prove that the fear is indeed excessive and unreasonable and thus the term "phobia" is not applicable."