The persistent, irrational fear that one’s romantic partner is being unfaithful, to the point that one’s daily routine is affected.
Example: A man has his wife followed and her phone bugged. After months of negative results, he cannot shake the idea that she has been unfaithful.
Grinnell, R. (2008). Pathological Jealousy. Psych Central. Retrieved on August 2, 2015, from http://psychcentral.com/encyclopedia/2008/pathological-jealousy/