More often than not, as far as train wrecks go, the ass end of a train wreck is arguably the most desirable position one might occupy whilst finding they are in the midst of a train wreck in process. The exception to this principle, of course, would be in the event that a train got ass wrecked. Even so, the ass-end of the offending party would most certainly fare significantly better than that of the violated party.
Boy: "Hey, Girl, did you have a rough night last night? You look like you just crawled out of the Ass End of a Train Wreck."
Girl: "Maybe so, but if you think I LOOK bad, I FEEL like that Train must have gotten Ass-Wrecked."
To Have furious Buttsex
To Just completely destroy your partners ass, making her bunghole many times the size it is normally, and making it completely wide enough to fit your fist.
Lebron: Hey Cockmonger, I asswrecked your mom last night!!