I'm going to have to be a bit pedantic here. The ISS is at an altitude where the air pressure is 10^-9 Torr, or about one ten-millionth as dense than the atmosp

I'm going to have to be a bit pedantic here. The ISS is at an altitude where the air pressure is 10^-9 Torr, or about one ten-millionth as dense than the atmosphere at the surface of the earth. In laboratory terms, that's an ultra high vacuum which only specialized facilities on earth can achieve. I think that calling it Vacuum is perfectly reasonable, unless your standard for vacuum is deep interstellar space?