The person has kindly posted the definition that they use to my journal. However, given the number of posts, people who are interested in seeing what the definition is, might not see it. Thus, I'm posting it here, but turning off comments for this post, as hopefully any further discussion can take place in the original post.
raveninthewind's definition of genslash:
This is slash in the sense that yes, there is m/m that is not canon, but it's less about the relationship than it is about the character. It's not a romance, in other words, but there is mention of m/m and m/f in the story.
I think there are many variant definitions, but that is mine. For example, I think the HP story is Lust Over Pendle is genslash.
I didn't make this term up, actually (it's been used before on LJ), but I don't care to debate whether anyone should use it. This is what i have to say; other people will add to the discussion, I am sure.