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.
Idioms, Informal Termslike mad,[Informal.]with great haste, impulsiveness, energy, or enthusiasm:She ran like mad to catch the bus.
Idiomsmad as a hatter, completely insane.
an angry or ill-tempered period, mood, or spell:The last time he had a mad on, it lasted for days.
[Archaic.]to make mad.
[Archaic.]to be, become, or act mad.
bef. 900; Middle English mad (adjective, adjectival), madden (intrans. verb, verbal, derivative of the adjective, adjectival); 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
1.See corresponding entry in Unabridged lunatic, maniacal, crazed, crazy.
2.See corresponding entry in Unabridged furious, exasperated, raging, wrathful, irate.
4.See corresponding entry in Unabridged 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.See corresponding entry in Unabridged frenzied.
4.See corresponding entry in Unabridged 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.