English▸ adjective
(madder, maddest)
2 mainly British mentally ill; insane:
he felt as if he were going mad.
▪ mainly British (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.
▪ in a frenzied mental or physical state:
she pictured loved ones mad with anxiety about her
it was a mad dash to get ready.
▪ (of a dog) rabid.
3 informal very enthusiastic about someone or something:
I wasn't mad about mountain bikes
[in combination] a sports-mad nation.
▪ British very exciting.
▸ adverb [as submodifier] US informal very; extremely:
he was mad cool—we immediately hit it off.
▸ verb
(mads, madding, madded)
[with object] archaic make mad or insane: had I but seen thy picture in this plight, it would have madded me.
– PHRASES
like mad informal
with great intensity, energy, or enthusiasm:
completely insane:
like mad informal
with great intensity, energy, or enthusiasm:
I ran like mad.
as mad as a hatter (also mad as a hatter) informal completely insane:
he's indisputably a genius, but he's also mad as a hatter.
[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.]
– ORIGIN Old English gemǣd(e)d ‘maddened’, participial form related to gemād ‘mad’, of Germanic origin.