What is Paranoia?

Legal Definition
Paranoia is a thought process believed to be heavily influenced by anxiety or fear, often to the point of delusion and irrationality. Paranoid thinking typically includes persecutory, or beliefs of conspiracy concerning a perceived threat towards oneself (e.g. "Everyone is out to get me"). Paranoia is distinct from phobias, which also involve irrational fear, but usually no blame. Making false accusations and the general distrust of others also frequently accompany paranoia. For example, an incident most people would view as an accident or coincidence, a paranoid person might believe was intentional.
-- Wikipedia
Legal Definition
the name that is given to the form of mental illness that is characterised by hallucinations, delusions and feeling of being persecuted.
Legal Definition
Same as Monomania See 158 N. Y. 558, 53 N. E. 29
-- Ballentine's Law Dictionary