dumpsturbation 

The act of pleasuring ones self (masturbation) whilst defecating (taking a shit).

Al had a dumpsturbation session on his lunch break....

dumpsturbation by Scottie2hottie82 October 1, 2010

Dumpsterbating 

The act of turning on the shower, then proceeded by sitting on the toilet and mastuerbating

"What we're you doing in the bathroom that took you like 2 hours?" "Dumpsterbating"

Dumpsterbating by Motodylan January 18, 2015