MAD is an acronym with several different uses in the English language and in its capitalized form is the name of a magazine which is popular among adolescents.

Common specific uses include:

• MAD Magazine
• Barajas International Airport (IATA Airport Code)
• MAD programming language (the Michigan Algorithm Decoder)
• Mutual assured destruction
• Magnetic anomaly detector

Also:

• Magnetic airborne detector
• Moroccan dirham (ISO currency code)
• MAD (Music-all-day) (Greek music channel)
• Militärischer Abschirmdienst (Military Counterintelligence of the German Bundeswehr)

It is also used as a truncation of madness.

A mad scientist is a scientist who works against typically held theories. The usually fictional scientists often have insane inventions that are covered up by either technobabble or the stereotypical quirkiness of scientists and engineers in their naming schemes. Real life "mad scientists" include:

• Nikola Tesla, who used the earth as a medium to transmit electrical power to any place in the world, as well as theoretical methods of mind control and death rays, but never completed his research on any for fear of his inventions being used for ill.
• The Wright Brothers, who succeeded in heavier-than-air flight which was before considered impossible by most people.

Mad is also used to describe rabies in animals; typically, but not limited to, mad dog and Bovine spongiform encephalopathy or mad cow disease.