When someone on facebook posts a status update that is actually part of a wall-to-wall conversation.
This usually results in the majority of the persons facebook friends to see one part of an incomplete conversation. Usually the comments on this update consist of "noob" or "learn to facebook nub", usually people just write "Fail", hence the term "Facefail".
"Person's status update: Ill see you tonight then heaps of love xxxxxxxxxxxxoooooooooxoxoxoxoxoxoxooxoxxxooxxo!!!!!
"P1: Hey remember that guy who posted that wall-to-wall conversation as a status update
P2:Yeah that was such a Facefail!!!"