What does the weight stat on weapons mean?
I can say after testing that it is knockback. I have used a Crystal Dagger which had weight 5. And most bats and especially ghosts where pretty much just knocked out of the screen.
It feels to me like beeing planed as advantage but in my opinion its actually a disadvantage.
I returned to even a weaker weapon without weight and getting along better with it.
So I can confirm as allready mentioned: weight means knockback.