There are 2 main definitions of mad in English:


Line breaks: mad

adjective (madder, maddest)

1chiefly British Mentally 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.
1.1chiefly British (Of behaviour or an idea) extremely foolish; not sensible: Antony’s mother told him he was mad to be leaving Dublin
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.
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 angry: don’t be mad at me
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, blazing, flaming mad, blazing mad, in a towering rage, incensed, wrathful, seeing red, cross, indignant, exasperated, irritated, berserk, out of control, beside oneself
informal livid, spare, wild, aerated
informal , dated waxy, in a wax
North American informal sore
become very angry, lose one's temper, get in a rage, rant, rant and rave, fulminate;
go crazy
British informal do one's nut
North American informal flip one's wig
vulgar slang go apeshit
1.4(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.
2 informal Very enthusiastic about someone or something: he’s mad about football [in combination]: another myth is that Scorpios are sex-mad
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.
informal crazy, potty, dotty, nuts, wild, hooked on, gone on
North American informal nutso
2.1British 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.
unrestrained, uncontrolled, uninhibited, wild, abandoned, overpowering, overwhelming, excited, frenzied, frantic, frenetic, ebullient, energetic, boisterous

verb (mads, madding, madded)

[with object] archaic Back to top  
Make (someone) mad: had I but seen thy picture in this plight, it would have madded me
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.


go mad

informal Allow oneself to get carried away by enthusiasm or excitement: let’s go mad and splash out
More example sentences
  • The audience went mad with excitement when the elephant stepped on to the stage.
  • Seeing their fans going mad as we played was one of the highlights of our time.
  • Keegan jogs out from behind the entrance curtains to the sound of Oasis classic ‘Rock and Roll Star’ and the home fans go mad for it.
become frenzied, become uncontrollable, lose control, erupt, boil over

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.
fast, furiously, as fast as possible, as fast as one's legs can carry one, hurriedly, quickly, rapidly, speedily, hastily
British informal , dated like billy-o

(as) mad as a hatter

informal Completely insane: he’s indisputably a genius, but he’s also mad as a hatter
[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.

mad keen

British informal Extremely enthusiastic: some men are mad keen on football
More example sentences
  • The Namibians are mad keen anglers and are extremely knowledgeable, competent, kind, helpful and dedicated to giving their clients the best possible trip.
  • Tony Heart is himself a mad keen angler and he works extremely hard at putting his anglers over the abundant quality fish; his spacious boat is purpose built for angling and cruises effortlessly at 14/15 knots.
  • You're mad keen on history - what's your favourite fact about London's past?

Definition of mad in:

There are 2 main definitions of mad in English:


Syllabification: MAD

Entry from US English dictionary


Mutual assured destruction.

Definition of mad in: