Top definition
the act of cupping one's hand over you butthole in the shower and letting the water run down your back and collect in your hand, then farting thus making a loud funny noise.
"i committed an Underwater Holocaust in the shower this morning, and it was so loud that my mom heard it and yelled at me. Heehee"
by toni pepporonni November 18, 2011
Get the mug
Get a Underwater Holocaust mug for your guy Bob.