1. Phrase used to question the wisdom of a smartass trying to pass off infomation on a topic you know the person knows little or nothing about.

2.Can also be used to change the subject.

Versatile phrase used as a put down.
> Guy 1: I think I need more fiber in my diet because I only shit once a day and my ass bleeds.
> Guy 2: What are you an ass[ologist]? or
> What are you a colon[ologist]? or
> What are you a fiber[ologist]? or
> What are you an assbleed[ologist]? etc.