A Phobia is a strong fear, oftentimes irrational. Examples include range from normal fears such as claustrophobia 'fear of enclosed places' and arachnophobia 'fear of spiders' to the unusual and.. downright spectacular fears such as Euphobia 'fear of hearing good news' and Ithyphallophobia 'fear of having an erect penis'.
Phobias can include practically any situation or object or group of people.
A List of Phobia's 
Wikipedia's page defining phobia's.