Photobomb to drop in a photo unexpectedly...to hop in a picture right before it is taken.
sarah: hey why is jimmy in the background of our prom picture?
ryan: idk, he must have photobombed it at the last second.
An otherwise normal photo that has been ruined or spoiled by someone who was not supposed to be in the photograph.
The most common photobomb is someone in the background making a face.
