When you stick your finger up someone's ass so deep you reach there intestine track, then your finger proceeds to slide and do loop de loops in there intestines
When you are completely naked and cover yourself in Italian olive oil before you run down the dorm hallway and see how far you can slide on your stomach. If not carefully lathered, the penis can catch and screech before tearing totally off resulting in a penisless man.
It was midnight last night and when I came out of the bathroom Logan was doing the NellySlide all the way from room 226 to 214