I see the term tossed around a lot but without a solid definition. Rather than calling a person as a casual gamer per say I see it as applied to the activity the person is doing at the moment.
For myself I think of activities like wondering the open world doing events and farming as more casual gaming. On the other hand doing the game story, raids, fractals, PvP and WvW more depth and not casual at all. Basically I think any kind of activity in the game that you can drop at a moment's notice as a casual activity. A player may do casual activities one day and more dedicated another. I doubt a truly casual gamer would touch MMOs much as by nature MMOs require a certain amount of dedication.
What do you think casual gaming and gamer is? Do you define yourself as a causal gamer? If so why?