sorrynotsorry is a term used by someone usually unhappy with someone because they are thought to have done something wrong. They use this term as if to say "What I did wasn't wrong so Sorry, I'm not sorry". It is often "hashtaged" on the social networking website Twitter.
Craig: "You're holding that pencil wrong"
Mike: "I didn't know there was a correct way to hold a pencil. sorrynotsorry"