When you have sex with a girl in the anus when she has the squirts, and when you pound them cakes she poops on your Ding Dong!!
"I was jammin Amanda's Hershey Highway and the dirty ho-bag didn't tell me she had been fighting the poop monster all day and she gave me a damn Butt-Chalupa!!"
by David Meece January 5, 2006
Get the Butt-chalupamug.