A fork of Rural Dictionary
When you post a status and your (or your friend's) mom adds a comment that completely hijacks the status to the point where the topic has changed.
You - "OMG, I totally had the worst day! I fell and broke my leg!" Mom - "Hey, since you're home, would you please record Dancing With The Stars for me tonight?" Everyone else - "OMG, I hope Derek Hough wins that Mirror Ball trophy!" You - "Thanks, mom. You just mom-jacked my pain."