someone who's general persona is on the mad side of normal. usually gets involved in acts of lunacy when intoxicated. these people usually deny the extent of their clinical insanity and try to find people who are more clinical than them, or at least claim that others are more mad.
gabe: tom is clinically insane
Gabe: cos all he ever goes on about is how crazy everyone else is and last night he went and blew his last 150 pounds on hookers, he even spent twenty on talking to them after hed finished
Pete: yeah thats clinical
someone who has lost the plot. mild case of insanity. does unexplainable things usually when intoxicated
dave: did you see what tom did last nite
joe: i no i cant believe he tried shagging a tin of beans
dave: hes nicked in the head man, he doesnt know what hes doing after a few beers