Photobomb
To pose in the background of a picture being taken
Example
We had one picture where we're all smiling but Jack had to go and photobomb it!

Benedict Cumberbatch photobombing U2 at the 86th Academy Awards
Related Slang
Selfie | A picture of yourself |
pic | Picture |
phobar | Photoshopped beyond all recognition |
pix | Pictures |
awks | Awkward |
An action popular among younger people; commonly involves a nice picture being taken of the subjects but somebody slips in the background with a goofy or creepy facial expression or awkward body pose.