I was reading about this the other day and even the people who call it a genocide tend to use a much, much more expansive definition of the term. Apparently it was the original definition, and under the original definition you didn't have to try to kill all of an ethnic group, just some part of it. The more widely accepted definition is that genocide is when you're attempting to kill or otherwise destroy an entire ethnicity root and branch. Several scholars pointed out that if you used the more expansive definition of genocide you'd have to include many other mass killings, including notably the nuclear bombings of Japan and a bunch of other things I can't remember, with the point being that the expansive meaning of genocide becomes vague enough to have no real purpose.