A rebuke or scolding delivered via social media platforms such as Facebook. Intended by the giver to cause ebarra*sment. Facebukes are characterized by their self-righteous nature, public delivery (when a private message would have been more than sufficient), lack of anonymity (as opposed to posting an anonymous comment to a blog, for example), and reluctance to engage in an intellectual debate around the topic. Usual perpetrators of the Facebuke are religious legalists looking to foist their particular idiosyncratic understandings upon others. Also known as an ebuke.
Dude, that guy who told you that you shouldn't listen to rock music on your wall totally Facebuked you.