Specific phobia refers to a marked irrational, unabating and persistent Fear of clearly discernible, noticeable, observable, or perceptible, circumscribed objects, activities or situations.

It is a fear of objects or situations which a person is capable of being perceived and noticed clearly.
Other /More definition:
Specific Phobia refers to a strong and irrational fear of a given object or situation.
Other /More definition:
specific phobia refers to unreasonable fear of a specific object or situation that markedly interferes with daily life functioning.