1. When the head of the pecker protrudes into the shaft creating a image like a turtles head hiding in its shell.
“As the winter began in pecker town, all the men started to feel a strange sensation. Owen asked why his weiner appeared to look like a turtle hiding in his shell. Vagman, (the man with the 12 inch shlong) Shouted, Hahahaha you have a nice nested turtle going.”
An adjective used to describe a male/female who has become so obsessed with their partner, they proceed to want to spend every minute of every day with them and talk about them non stop.
Jacob: "I met this girl the other day she's absolutely wonderful I think I want to take her on countless dates and end up marrying her with 3 children....."
Friend: "Please stop talking about her"
Jacob: "But I have to tell you as much about her as humanly possible"
Friend: "Jacob stop being a NestingTurtle and keep it to yourself!"