Mass encompasses anything that is not fat (blood, bone, cartilage, ligament, muscle, etc and includes water).
In order to put on mass (lean body tissue) you have to eat in excess of what is needed caloricly to maintain your current LBM (lean body mass). There's a quick way and and a slow way. Eating up to 20% over your maint in clean food would constitute a slow method in my book.
Eating radically over in any food (quarter pounders, hot dogs, BK double stacks, etc) is a fast way, but guarantees you'll put on a lot of fat.
It comes down to this: If you're competing in a BB contest, then do it the fast and dirty way. It requires more discipline when you switch to cutting, but it's faster.
For the everyday guy, I simply don't see the need for dirty bulking. Just eat a healthy diet with a balance protein, fat and carbs, with lots of vegetables (the veggies help maintain LBM and non-muscular connective tissue), have a PWO protein drink and you'll be fine.