Term used to describe a state of being off of the internet, no Facebook, Twitter, Skype, AIM, Gmail chat, Myspace etc. The only exception being e-mail and phone calls (only school/work related). Generally used in cases of drama-overdose.
"My dog died yesterday, and my boyfriend just dumped me so I'm going off-grid, guys. Call me."
"That bitch is totally cyber-bullying me so I'm going off-grid until that chick cools off."