When a person gets so hot that a tiny sweat resevoir forms at the small of their back. Once it reaches full capacity it begins to trickle or flow down the natural crevice tween one's ham hocks (buttocks)
"Dude! I was so sweaty from rollerblading! Springtime came early and I had a buttcheek waterfall ... Yosemite-style-Yo!"
After a long day, your sack begins to sag and slowly nestles its warm elasticity tween your legs. After an hour or two it begins to itch. So one must casually reach below and yank it up out of the crotch nest. This is the nutsack shuffle. Also known as a "nutty shuffle, plucking the birds nest and juggling"
Yo, I had to pull a nutsack shuffle in front of my girlfriend's parents at the dinner table. My hand came back w/ 3 curlys.