Originally meaning masturbation, though more recently used to describe any sort of activity, scandalous or not.
I caught my little brother smacking toboggan!
"What up mang?"
"Not much broseph, just smacking toboggan."
The band Senses Fail released their Let It Enfold You album with a bonus disc which included a short history and compilation of their early years, "smacking toboggan" is referenced there.