There's a clinical psychologist that describes it as a disorder in large part characterized by a lack of executive function. In other words, you can't necessarily make yourself do what you're supposed to unless you have a desire to do it. So your desires tend to take priority or distract from your wants or needs. And obviously like all disorders it has to be debilitating to some degree–usually interference with two or more areas in your life (home, professional, school, etc.).
