1. a person who deliberately appears in the background of someone else's photograph, typically without permission or awareness
Usage: informal; often used humorously

Examples

• A photobomber jumped into the frame just as we took our family portrait.
• The wedding photographer had to retake several shots because of photobombers in the background.
• He became famous on social media for being a serial photobomber at tourist attractions.
• The photobomber made a silly face behind the couple during their engagement photo session.
• We didn't notice the photobomber until we looked at the pictures later that evening.