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.
Specific uses include:
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 technobable or the stereotypical quirkiness of scientists and engineers in their naming schemes. Real life Mad Scientists include:
Mad is also used to describe rabies in animals, typically, but not limited to, Mad Dog; and Bovine spongiform encephalopathy or Mad Cow Disease.