Just me, but I think of 20 pounds of gear or less for fully self supported touring to be light touring. At 15 pounds or less of gear, again self supported, I consider it ultralight.

I personally don't apply the terms light or ultralight to supported tours or credit card tours which by their nature generally don't involve carrying much.

There are no rules and no general agreement so feel free to draw those lines where ever you want, but I think that the weights I mentioned are reasonable.