The act of fornication as carried out on a sled speeding down a hill. Sledding on a steep incline is not recommended, and the participants risk the threat of serious injury. Just another way to heat up your sex life in those chilly winter months. Common in Norway.
Sledder 1: What the fuck is on that sled?
Sledder 2: Oh, just your aunt and uncle alpine slucking.
Sledder 1: ...