I think of "light" touring not so much about a specific weight but as the general idea that you will be carrying less than a "fully loaded" touring load because you will likely not be camping and/or not be cooking.

But I could be wrong about that.

Perhaps in contradiction with definition, I consider "ultra-light" touring to be a minimalist form of touring where it's not so much about where you will or won't be sleeping and where your food comes from so much as it's about trimming your gear down to the minimum.

When it comes to overnight camping trips, I tend to take more than I would on a multi-day tour simply because know that it won't be day after day of lugging this or that piece of gear. The amount of time spent at a campsite has more impact on my packing than gear weight. If I know that every camp is just a temporary stop for the night, I try to streamline my gear to the essentials. If I plan to spend a fair amount of time at camp, extras start to creep in: Cooler, chair, frisbee, etc.