Hot, but mean-spirited, almost violent sex used to punish someone. Sometimes it's used to get back at a significant other. Sometimes it's used to make the significant other wake up with scars, bruises, and/or the inability to walk straight.
She's hot but annoying. I wanna grudge fuck her into traction.
Wild and vigorous sex done with the intention of putting the other person through the wall. The wall may be literal or metaphorical. The point is to fuck the person hard, deep, and with quick, almost violent strokes. Despite the nature, the slamfuck is usually done with good intentions.
What a freak! Don't go in for that nice and gentle shit. She likes a good, hard slamfucking.