An activity that involves limited movement, effort, or thought to accomplish. Often associated with the role of a Reddit Moderator or similar internet "jobs". In particular, a Marsden Activity involves some sort of technology holding the attention of the culprit for numerous hours at a time.
Person 1: Oh I've been so unproductive, all I've done today is lay in bed and watch TV
Person 2: That's the biggest Marsden Activity I've ever heard
Person 1: And I didn't have enough time to cook dinner so I ordered too much junk food!
Person 2: These Marsden Activities are stacking!