1. To appear in someone else's photo without thier permission, often pulling a stupid or offensive pose. Best done in a dark club where the deed can't necessarily be detected until the photo is viewed, by which time a speedy escape has already been made.
2. To jump in front of a camera as someone is taking a picture of someone/thing else. Worsks especially well on tourists in foreign cities.
Often causes frustration and annoyance to the victim(s) but great amusement to the perpetrator and thier peers.
"Remember that bunch of gimps in the club last night? I photojacked them a goodun! Ninja style too!"
"Dude! I can't believe it! I was taking a photo of my fellow tourist, Wing Shing Li, in front of Big Ben and someone Photojacked me! It was my last picture too!"