A Facebook friend that you do not know, and only added them because of mutual friends. Usually done to beef up one's profile.
DAVID: "Sean Westford" hhmm, 146 friends in common, I'll add him with a friend request
. SEAN: *IGNORE* David:*Sends Message* "Dude did you ignore my friend request" Sean: I don't want a Facebook
Friend, not a Facebook aquaintance