The act of going on Facebook and untagging yourself from incriminating photos. Whether it be cause your parents are getting a Facebook or you just don't want people to see you in embarrassing pictures from last night.
You: "Wow ..my mom is getting a Facebook"
Friend: "Haha, Dude that sucks, you have so many messed up pictures"
You: "Tell me about it, I'm gonna have to go on an untagging spree"
Person a: Why were you in the toilet for so long?
Person b: sorry man, was unclogging the pipes.
Person a: That's disgusting.
(Applies to both definitions)