The remains of a living thing after being hit by a train. The meat remains left behind by a train can resemble ground sausage: therefore, it is called train sausage.
When traversing a zombie-filled subway, stay off the tracks to avoid being train sausage'd.
While travelling the Tundra Express, always mind your surroundings. Trains love to sneak up on you and turn you into train sausage.
When you find out a guy has already slept with a close friend. (male or female, it's still sausage)
See Tainted Beef for a woman.
Dude 1 'Dude, I was gona sleep with Kyle, but then I found outyou already had'
Dudette 1 'Ah man that sucks, doesn't matter though, he was tepid at best'
Dude 2 ' When a friend taints your prospect sausage it hurts hard, ahh... Tainted Sausage'