When you go to hug a person that is unsure if they want to hug you but you force the hug. While the hug is awkward you try to re-adjust leading to much more awkwardness than you bargained for.
John was really nervous on his first date with Jenn. When it was time to leave the restaurant he went in for a hug while Jenn was going for a hand shake. He then tried a re-hug which lead to even more awkwardness. They both wish the incident would have never happened.