A stock character in popular fiction; a bumbling scientist working on unlikely ways to save the world, or a villainous one bent on destroying it.

(uncountable, by ellipsis) Mad cow disease; bovine spongiform encephalopathy. / (countable) A cow afflicted with mad cow disease. / Used other than figuratively or idiomatically: see mad, cow.

(idiomatic) Extremely angry; furious to the point of outburst.

Alternative spelling of madman

Madness attributable to the heat of summer, or to the midsummer moon.

(idiomatic) A sum of money, often relatively small in amount, kept in reserve to use for impulsive, frivolous purposes.

Demented or crazy.

(intransitive) To become insane. / (intransitive, informal, typically followed by "and" and a second verb) To do something extravagant.

plural of mad scientist

(slang) Demented, crazy.