adjective, madder, maddest.
mentally disturbed; deranged; insane; demented.
enraged; greatly provoked or irritated; angry.
abnormally furious; ferocious: a mad bull.
affected with rabies; rabid: a mad dog.
extremely foolish or unwise; imprudent; irrational: a mad scheme to invade France.
wildly excited or confused; frantic: mad haste.
overcome by desire, eagerness, enthusiasm, etc.; excessively or uncontrollably fond; infatuated: He's mad about the opera.
wildly gay or merry; enjoyably hilarious: to have a mad time at the Mardi Gras.
(of wind, storms, etc.) furious in violence: A mad gale swept across the channel.
an angry or ill-tempered period, mood, or spell: The last time he had a mad on, it lasted for days.
verb (used with object), madded, madding.
Archaic. to make mad.
verb (used without object), madded, madding.
Archaic. to be, become, or act mad.
like mad, Informal. with great haste, impulsiveness, energy, or enthusiasm: She ran like mad to catch the bus.
mad as a hatter, completely insane.

before 900; Middle English mad (adj.), madden (intransitive v., derivative of the adj.); Old English gemǣd(e)d, past participle of *gemǣdan to make mad, akin to gemād mad, foolish; cognate with Old Saxon gemēd, Old High German gimeit foolish

half-mad, adjective
half-madly, adverb
half-madness, noun
quasi-mad, adjective
quasi-madly, adverb
unmad, adjective
unmadded, adjective

1. lunatic, maniacal, crazed, crazy. 2. furious, exasperated, raging, wrathful, irate. 4. ill-advised; unsafe, dangerous, perilous. Mad, crazy, insane are used to characterize wildly impractical or foolish ideas, actions, etc. Mad suggests senselessness and excess: The scheme of buying the bridge was absolutely mad. In informal usage, crazy suggests recklessness and impracticality: a crazy young couple. Insane is used with some opprobrium to express unsoundness and possible harmfulness: The new traffic system is simply insane. 5. frenzied.

4. sensible, practical; sound, safe.

Mad meaning “enraged, angry” has been used since 1300, and this sense is a very common one. Because some teachers and usage critics insist that the only correct meaning of mad is “mentally disturbed, insane,” mad is often replaced by angry in formal contexts: The president is angry at Congress for overriding his veto. Unabridged

mad. Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2015.
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World English Dictionary
mad (mæd)
adj (foll by about, on, or over; often postpositive) , madder, maddest
1.  mentally deranged; insane
2.  senseless; foolish: a mad idea
3.  informal (often foll by at) angry; resentful
4.  wildly enthusiastic (about) or fond (of): mad about football; football-mad
5.  extremely excited or confused; frantic: a mad rush
6.  temporarily overpowered by violent reactions, emotions, etc: mad with grief
7.  of animals
 a.  unusually ferocious: a mad buffalo
 b.  afflicted with rabies
8.  informal like mad with great energy, enthusiasm, or haste; wildly
9.  mad as a hatter crazily eccentric
vb , madder, maddest, mads, madding, madded
10.  archaic to make or become mad; act or cause to act as if mad
[Old English gemǣded, past participle of gemǣdan to render insane; related to gemād insane, and to Old High German gimeit silly, crazy, Old Norse meitha to hurt, damage]

MAD (mæd)
n acronym for
mutual assured destruction: a theory of nuclear deterrence whereby each side in a conflict has the capacity to destroy the other in retaliation for a nuclear attack

Collins English Dictionary - Complete & Unabridged 10th Edition
2009 © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009
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Word Origin & History

O.E. gemædde (pl.) "out of one's mind" (usually implying also violent excitement), also "foolish," earlier gemæded "rendered insane," pp. of a lost verb *gemædan "to make insane or foolish" (related to gemad "mad"), from P.Gmc. *ga-maid-jan, demonstrative form of *ga-maid-az "changed
(for the worse), abnormal" (cf. O.S. gimed "foolish," O.H.G. gimeit "foolish, vain, boastful," Goth. gamaiþs "crippled, wounded," O.N. meiða "to hurt, maim"), from intensive prefix *ga- + PIE *moito-, pp. of base *mei- "to change" (cf. L. mutare "to change," mutuus "done in exchange," migrare "to change one's place of residence;" see mutable). Emerged in M.E. to replace the more usual O.E. word, wod (see wood (adj.)). Sense of "beside oneself with excitement or enthusiasm" is from early 14c. Meaning "beside oneself with anger" is attested from c.1300, but deplored by Rev. John Witherspoon (1781) as an Americanism, and now competes in Amer.Eng. with angry for this sense. Of dogs, "affected with rabies," from 1800. Phrase mad as a March hare is attested from 1520s, via notion of breeding season; mad as a hatter (1857) is said to be from erratic behavior caused by prolonged exposure to poison mercuric nitrate, used in making felt hats. Mad as a wet hen is from 1823. Mad money is attested from 1922; mad scientist is from 1940.
Online Etymology Dictionary, © 2010 Douglas Harper
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American Heritage
Medical Dictionary

mad (mād)

  1. Angry; resentful.

  2. Suffering from a disorder of the mind; insane.

  3. Affected by rabies; rabid.

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

MAD definition

1. Michigan Algorithm Decoder.
2. A data flow language.
["Implementation of Data Structures on a Data Flow Computer", D.L. Bowen, Ph.D. Thesis, Victoria U Manchester, Apr 1981].

The Free On-line Dictionary of Computing, © Denis Howe 2010
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American Heritage
Abbreviations & Acronyms
  1. Barajas Airport (Madrid, Spain)

  2. Morocco—dirham (currency)

  3. mutually assured destruction

  1. Madagascar

  2. madam

The American Heritage® Abbreviations Dictionary, Third Edition
Copyright © 2005 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
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American Heritage
Idioms & Phrases


In addition to the idioms beginning with mad, also see crazy (mad) about; drive someone crazy (mad); hopping mad; like crazy (mad); stark raving mad.

The American Heritage® Dictionary of Idioms by Christine Ammer.
Copyright © 1997. Published by Houghton Mifflin.
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Example sentences
To many, they are a snaggletoothed symbol of big government gone mad.
Tell me a tale about animals who really are people and make a princess mad.
Fall asleep at your desk for five minutes---then the boss gets mad.
Fill a few with dry ice to turn your house into a mad scientist's laboratory.
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