What do you call a person who has irrational fear? Its about abnormal psychology.

Irrational fear, I guess would be called paranoia.

A phobia is an irrational fear of something.

How about neurotic?

Hm, neurotic is out of use in favor of specific diagnosis. Too much fear and anxiety would be an anxiety disorder of some kind from very serious to non-psychotic cases of "nerves".

Yes a "phobia" is an irrational fear such as "clostrophobia" - fear of close , tight quarters or environments.