The tracks of a promiscuous biddy left on the floor following a night of drunken copulation. The trail is usually most visible at the beginning (near the bedroom) and dissipates towards the backdoor. The origin of the trail comes from the biddies' vagina; which is so loose, it hangs to the floor.
Tommy: "That girl that Danny had over last night was disgusting!"
Stanley: "Ya, I know. I stepped through her slug trail on the way to the bathroom this morning."