Similar to a bathroom buddy. It's when two or more girls who regularly go to the bathroom together when out in a public place, also seem to be online at the same time on facebook.
"Amanda and Christie went to the bathroom together at the bar the other night and I always seem to see them on at the same time on facebook."

"So they're each others facebook buddy?"

"Bingo."
by Flirbertz (M.Richie) November 12, 2009
Get the facebook buddy mug.
A Facebook buddy is someone whom you've added as a friend on the website Facebook and when in conversation, one will say that he or she is a friend; when in actuality, you would never trust them to open a can of beans. In addition, a Facebook buddy is someone who you would never invite to your house, and is constantly forced to make small talk with.
So Dave, you've been making friends in the company?

Yeah......sort of.

Hey...what about Jenna down the hall. you've added her on Facebook right? You guys are becoming good friends.

Yeah, I would like to think that, but she's just a Facebook buddy.
by Kyle Reed from the North October 28, 2008
Get the Facebook Buddy mug.