Chatanooga Choo Choo
When someone squats over the chestal section of a person and proceeds to have the runs on their chest and continues down to their lower reigons.  Thus creating a "train" of poop down their entire abdominal area.
Last night I was gonna give my girlfriend a cleaveland steamer but since I had the shits it quickly turned into a chatanooga choo choo.  Whoo Whoo!

OR

Pardon me ladies, which one of you would like to get a ride from the Chatanooga Choo Choo?  Whoo Whoo!