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[dih-men-tid] /dɪˈmɛn tɪd/
crazy; insane; mad.
affected with dementia.
Origin of demented
1635-45; dement + -ed2
Related forms
dementedly, adverb
dementedness, noun
half-demented, adjective
semidemented, adjective
1. lunatic, crazed, deranged, unbalanced.


[dih-ment] /dɪˈmɛnt/
verb (used with object), Obsolete
to make mad or insane.
1535-45; < Late Latin dēmentāre to deprive of mind, equivalent to Latin dēment- (stem of dēmēns) out of one's mind (dē- de- + ment- (stem of mēns) mind) + -āre infinitive suffix Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2015.
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Examples from the Web for demented
Contemporary Examples
Historical Examples
  • He was very wistful and very eager, and said I must not think him a fool or demented.

  • She appeared to be demented, and sang snatches of savage songs.

    Chronicles of Border Warfare Alexander Scott Withers
  • Louis, as I was saying, regards the man in the romantic light of a humanitarian monomaniac or a demented food reformer.

    Max Carrados Ernest Bramah
  • But at that moment the young lady rose and ran as if demented into her castle.

    The Burning Spear John Galsworthy
  • I vaguely recall roaming like a demented being among those solitudes in search of water, and finding a boiling spring.

    The Moon Rock Arthur J. Rees
British Dictionary definitions for demented


mad; insane
Derived Forms
dementedly, adverb
dementedness, noun


(intransitive) to deteriorate mentally, esp because of old age
(transitive) (rare) to drive mad; make insane
Word Origin
C16: from Late Latin dēmentāre to drive mad, from Latin de- + mēns mind
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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Word Origin and History for demented

1640s, from obsolete dement "drive mad."



1540s, "to drive mad," probably from Middle French démenter, from Late Latin dementare "to drive out of one's mind," from phrase de mente (a less technical term than insanitas), from de + mente, ablative of mens mind" (see mind (n.)).

Online Etymology Dictionary, © 2010 Douglas Harper
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demented in Medicine

demented de·ment·ed (dĭ-měn'tĭd)

  1. Mentally ill; insane.

  2. Suffering from dementia.

The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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demented in Technology

Yet another term of disgust used to describe a program. The connotation in this case is that the program works as designed, but the design is bad. Said, for example, of a program that generates large numbers of meaningless error messages, implying that it is on the brink of imminent collapse.
[Jargon File]

The Free On-line Dictionary of Computing, © Denis Howe 2010
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