I'm always amused by the language of debate and find that many of the definitions - as they are explained - amusing, indeed -- amusing in a good, healthy way, and not demeaning to anyone here.
Pehaps we should be thankful for
Theodore Sturgeon's definition (paraphrased):
"Science Fiction is what you find in the library marked 'Science Fiction'." 
I still want to be amused, however, so I'm waiting for more definitions to follow. I'm surprised, though, that no one has shaken this moth-eaten carpet out the window to air:
"Science Fiction is just technological Fantasy."
Don