When you're banging a girl doggy style and she's about to climax, grab her by the ankles, stand her on her head and cram your fist down her dank exit hole, thus ruining her orgasm.
Also see Inverted Particle Accelerator for more sexually deviant partners.
A showstopper is a lady who is so exquisitely beautiful, so flawlessly graceful, and so sentillatingly sexy...that everything and everybody stops, when she appears!
The Sheboygan Showstopper is a sexual act in which the man inserts his penis and testicles inside a woman's (or man's) anus. The testicles will often become stuck inside the anus.
We were having butt sex when I accidentally gave her the Sheboygan Showstopper. I couldn't get my sack back out.
I needed to get home to have dinner with my mother so I ended her with a Sheboygan Showstopper