1. A psychotic disorder characterized by delusions of persecution with or without grandeur, often strenuously defended with apparent logic and reason.
2. Extreme, irrational distrust of others.

[Greek, madness, from paranoos, demented : para-, beyond; see para-¹ + nous, noos, mind.]

The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.