Real Dictionary

mad
adjective: Someone who is mad has a mind that does not work in a normal way, with the result that their behaviour is very strange.

MAD in American English
the theory that the possession of equally devastating nuclear weapons by superpowers will deter each from attacking another or its allies
adjective: severely mentally disturbed
intransitive verb: to be, become, or act mad
noun
noun: an angry or ill-tempered period, mood, or spell
transitive verb: to make mad

mad in British English
adjective: severely mentally ill, so that normal thinking and behaviour is impossible
noun acronym for: mutual assured destruction: a theory of nuclear deterrence whereby each side in a conflict has the capacity to destroy the other in retaliation for a nuclear attack

mad. in American English
madam