There are 2 main definitions of mad in English:


Syllabification: mad

adjective (madder, maddest)

1Mentally ill; insane: he felt as if he were going mad
More example sentences
  • The household is mad, disturbed, yet idyllic and peaceful.
  • Posterity has called her mad: a schizophrenic.
  • He described him as completely mad, crazy, off the wall.
1.1(Of a person, conduct, or an idea) extremely foolish or ill-advised: they were all mad to go believing such a cock-and-bull story
More example sentences
  • The reader isn't expected to take anything on faith or invest belief in any seemingly mad ideas, which is probably just the right tone for this sort of introductory book.
  • When I visited her, I saw notebooks full of her mad ideas.
  • There's no secret code or literary illusion, there's just his own mad thoughts on a page.
foolish, insane, stupid, lunatic, foolhardy, idiotic, senseless, absurd, impractical, silly, inane, asinine, wild, unwise, imprudent
1.2In a frenzied mental or physical state: she pictured loved ones mad with anxiety about her it was a mad dash to get ready
More example sentences
  • Lela looked up, trying to hide her amusement as they saw Stasia, obviously driven mad with jealousy and defeat, throwing random sculptures at the two.
  • Everyone in the paper ticket line makes a mad dash back to the kiosks.
  • The dance started at seven so there was a mad scramble to get ready.
1.3 informal Very enthusiastic about someone or something: I wasn’t mad about mountain bikes [in combination]: a sports-mad nation
More example sentences
  • When it comes to sports, India is mad about cricket.
  • Peter was extremely proud of his children and very happy with Kayce, who took care of him, who protected him, who was just mad about him.
  • With every sigh, I become more mad about you, more lost without you.
enthusiastic about, passionate about;
ardent about, fervent about, avid about, fanatical about;
devoted to, infatuated with, in love with, hot for
informal crazy about, nuts about, wild about, hooked on, gone on, nutso about
1.4 informal Very angry: they were mad at each other
More example sentences
  • Now don't be mad with me, because it's not entirely my fault that this is happening.
  • If you put in the wrong directions, people get quite mad at you.
  • How could I be mad at you for defending yourself?
angry, furious, infuriated, irate, raging, enraged, fuming, incensed, seeing red, beside oneself
informal livid, sore
literary wrathful
(get mad)lose one's temper, get in a rage, rant and rave
informal explode, go off the deep end, go ape, flip, flip out, flip one's wig
1.5(Of a dog) rabid.
More example sentences
  • This is the ‘furious’ form of rabies, the kind traditionally associated with mad dogs.
  • I don't have a nail gun but I've used one from a local shop to knock together a gate and a retaining wall that didn't restrain Holly the mad dog.
  • Then the restrained growl of a mad dog found its way past her curled lips, rasping at the stranger before her who hadn't flinched.
1.6British informal Very exciting.
More example sentences
  • The finale to our visit came the very next evening when we were taken on a VIP visit to the Regency Casino for a mad night of wild abandon at the slot machines.
  • In the audience it was both a mad mayhem of frenetic bouncing and a sea of staring faces intrigued and in awe.
  • I had a sudden uncontrollable desire to be in some mad city on the other side of the world again.

verb (mads, madding, madded)

[with object] archaic Back to top  
Make mad or insane.
More example sentences
  • A wise citizen, I know not whence, had a scold to his wife: when she brawled, he played on his drum, and by that means madded her more, because she saw that he would not be moved.
  • For Mrs. Bleecker was very wrathful, Euan, and Lana's indiscretions madded her.


Old English gemǣd(e)d 'maddened', participial form related to gemād 'mad', of Germanic origin.


like mad

informal With great intensity, energy, or enthusiasm: I ran like mad
More example sentences
  • My eyes are hurting like mad, this means I will probably have a cold soon.
  • On Saturday morning every bone and muscle was hurting like mad but we still had to soldier on.
  • The two looked at each other for a second, then fired like crazy and ran like mad.

(as) mad as a hatter

informal Completely crazy.
[with reference to Lewis Carroll's character the Mad Hatter in Alice's Adventures in Wonderland (1865), the allusion being to the effects of mercury poisoning from the use of mercurous nitrate in the manufacture of felt hats]
More example sentences
  • She's mad as a hatter but that bunch of loonies will love her.
  • ‘He is as mad as a hatter and in to everything,’ said friend Lesley Gill, who used to work with Brian in the Newbridge branch of Dunnes Stores.
  • As long as you temper your unrestrained approach to life with occasional periods of sanity - and do your best not to get arrested - it's completely acceptable to be as mad as a hatter.

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