Fucked hard, vigorously beyond all possible terms. The slader is sweating bullets and experiencing the best sex of his life, while the sladee is getting her brians fucked out. Some entitle it hardcore sex, it can involve bondage, fisting, anal, whatever one feels like doing. Put blunly, the kinkiest, rudest, most gut wrenching, exasusting, tiring, hardcore sex of one's life.
You: "Dude, did you hear? Jennifer got sladed by Mike last night."
Friend: "Woah, I bet her pussy is torn to shreds."