Its a double walled tent. Yes, tent+fly=double-wall.

no, a tent and fly toegether = tent and fly and not double wall. a true double wall has 2 layers of fabric sewn together at the edges at a min. sort of like a sleeping bag has an inner and outer shell. adding a fly means that you now have a tent with a fly.

I'm with knanier on this one.

"By simple definition a double wall tent uses a rainfly over the tent, whereas a single wall tent does not." -about.com

"The term “double-wall” refers to tents which have a tent body supported by poles running
through sleeves or to clips, and a separate rain fly over the top of the pole structure." -Marmot

I would like to know what tent jg is referring to for his "double wall" definition. I can't think of a single tent like to one he is describing.

Single wall example = Mountain Hardware EV3
Double wall example = any tent with a rain fly