The flap of skin inside a mans scrotum, a hole/cavity which is located underneath the base of the penis slightly off to the left/right side. See if you can find it by making a hook with your finger and just below the base of your penis by the side off to the left/right press against your scrotum and pull up-wards. (you may have to wiggle your finger a bit to get it in)
Verb: to motorboat someone's ball sac as though it were a woman's cleavage. Scrotorboating is not exclusive to the nuts, and can even include said activity on someone's taint.
Taking a picture of your nuts on a friend's cell phone and setting it as their wallpaper. The next time they open their phone they have a virtual teabag.
"I gave Cindy a scrotorola. Somebody call her and make her pick up her phone..."