Something that is a typical example (or a 'textbook' example) of something such as a symptom of an illness (e.g. a runny nose & a high temperature) which often presented to a medical clinic is easily diagnosed. Clinical may be a synonym for 'textbook' or 'textbook case'.
An WOW addict quits playing because he determined it was ruining his life and a few weeks later begins heavily playing some other MMO game - That's Clinical - a clear example of (in this case) an addictive personality who needs help
by Cookie1224 December 09, 2011