Tarzanello's definitions
When one person shits in the water tank, preferably onto the ballcock, while receiving oral sex from a partner who is sitting on the toilet, AC Slater style, also taking a shit.
So I went to leave an Upper Decker in Bill's toilet, but Mary came in and offered to give me a Double Blumperdecker since she had to shit, too.
by Tarzanello April 1, 2015
Get the Double Blumperdeckermug.