A relatively new practise where someone (usually a pervy guy) takes pictures up a girls skirt unbeknownst to her using his mobile phone or camera. You can find pictures of this kind published on the internet. There's a theory that it's the act of taking the picture whilst the victim is unaware that gives the photographer the thrill, and not in fact the poor quality photograph it results in.
"Why is that guy holding his hand out and grinning?"
"See that girl with the short skirt standing next to him? He's upskirting"