When you are sitting on the toilet and someone comes up and flushes it before you are done pooping. You then can feel a moist breeze on your nuts.
Everything was coming out just fine until she sneaked up and gave me a Tropic Thunder from Down Under. I was unable to get off the toilet since I was not finished dropping my load. The cool breeze did feel nice on my balls though.
by Titanium NT December 1, 2009
 Get the Tropic Thunder from Down Undermug.
Get the Tropic Thunder from Down Undermug.