Definition of "derange" [de•range]

• To disturb the order or arrangement of. (verb-transitive)
• To upset the normal condition or functioning of. (verb-transitive)
• To disturb mentally; make insane. (verb-transitive)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "Absolute knowledge, by contrast, is not total but unconditional knowledge, the following of a particular direction or connection for its own sake, without regard for its potential to "derange" the whole (Schelling, First Outline 26)."
• "The first example given for "derange" in the OED that fits the meaning "to disorder the mind of, unsettle the reason of" is from 1825 "The trouble which our youth was thought to bear With such indifference hath deranged his head.""
• "She could see that he really was grieved to 'derange' her, but that circumstances pressed."