A replacement for foul curse words, it's a combination of crazy and drunk, meaning crazy drunk (which also refers to people who are high). It also means something at a high level (for example, volume) or to have a good time.
Historical perspective: Originally a style of rap music popular in the South, this term was popularized by a joke on Conan O'Brien.
See also : meh  
NetLingo Classification: Online Jargon