Can compulsions be defined in a way that is independent of obsessions, culture, etc? DSM-V defines compulsions (as part of OCD) and then adds a bunch of qualifications.  I wonder if we can define compulsions in a more objective way.  Compulsions are repetitive behavior/thoughts intended to reduce distress and/or prevent a potentially serious situation.  In this way they are different from other repetitive behavior, for instance, in autistic disorders.  

But this definition alone does not seem to be enough to distinguish compulsions from socially sanctioned and justified rituals and activities, be it praying for hours, working 16 hours a day, or whatever.  In addition, when we talk about compulsive gambling, shopping, gaming, TV watching, studying, eating, whatever, about people feeling "compelled" to do things in a certain rather rigid and repetitive way, how are we defining compulsions?  Is it about reduced wilfulness (as in addictive behavior)?  Is it about how irrational the behavior is (though it's hard to decide logically how we should live our life, as even philosophers can differ on this point)?  And so on.  

Thanks.
The fifth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) includes a new chapter on Obsessive-Compulsive and Related Disorders to reflect the increasing evidence of these disorders’ relatedness to one another and distinction from other anxiety disorders, as well as to help clinicians better identify and treat individuals suffering from these disorders.

You are right that compulsions are


  repetitive behavior/thoughts intended to reduce distress and/or
  prevent a potentially serious situation


and this definition can be used for compulsive behaviour which does not pose a problem.

In this chapter the DSM is talking about disorders which in turn means we are talking about unjustified or socially unacceptable behaviour.