Top definition
1. When you stumble upon the page of a person you haven't seen in years and find they've changed in shocking ways you would never expect

2. When you discover that people you know know other people you know without you knowing. Sometimes better than you'd like them to.

3. Generally when you see something surprising or unexpected about or involving people you even vaguely know, and it goes beyond the level of surprise to a state where your reality is totally rocked.
"Remember that really dorky girl everyone made fun of in school? Shes a rich supermodel now."

"Oh god, my current girlfriend and ex girlfriend are friends on facebook. They have loads of pictures together too, I think they're pretty close. She never told me they knew each other!"

"What a facebook mindfuck!"
by acitsAstica October 07, 2009
Happy St. Patties Day!
When you see a status, that simply mind fucks the shit out of you. Literally like you may catch aids without protection.
facebook mind fuck status- "its like an unstoppable force meeting an unmovable object"

unlikely victim of looking at the status, - bro, i think i just been mind fucked, i have aids...
by Izzytheshizzy December 26, 2011
Happy St. Patties Day!