Completely insane; crazy.
insane, mentally ill, certifiable, deranged, demented, of unsound mind, out of one's mind, not in one's right mind, sick in the head, not together, crazy, crazed, lunatic, non compos mentis, unbalanced, unhinged, unstable, disturbed, distracted, stark mad, manic, frenzied, raving, distraught, frantic, hysterical, delirious, psychotic, psychopathic, mad as a hatter, mad as a March hare, foaming at the mouth
- ‘he's indisputably a genius, but he's also mad as a hatter’
- ‘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.’
- ‘To prove there is nothing as mad as a hatter, Jane Bom-Bane unveils her Greatest Hats at The Shed, Brawby Village Hall, near Malton, on October 25.’
- ‘He has earned quite a reputation for being as mad as a hatter on the field.’
- ‘She's rude, insensitive, and quite possibly mad as a hatter.’
- ‘She received demented letters from a mental asylum escapee, and yet it was she who ended up mad as a hatter.’
- ‘‘Being John Malkovich ‘takes you into a tunnel where you crawl straight ahead on all fours toward a light, and you think maybe Lewis Carroll's waiting at the other end, because it's all very surreal and as mad as a hatter.’’
- ‘Robert Wade's father, the late Duke of Carnon, had been as mad as a hatter, as had two of his sisters.’
- ‘She was obviously as mad as a hatter was, and all I wanted to do now was to go home.’
Popularized with reference to Lewis Carroll's character the Hatter in Alice's Adventures in Wonderland (1865), although the phrase was first recorded in the 1820s; the allusion is to the effects of mercury poisoning from the former use of mercurous nitrate in the manufacture of felt hats.