Green’s Dictionary of Slang

to take a (snatched) photograph of a celebrity.

2006		Observer 16 Apr. 22/5: Or those photographers who hang around the Beach down in Fulham trying to pap me in the early hours.
2008		Daily Mirror 10 Jan. 33: Nicole is papped all the time.
2014		Sydney Morn. Herald 17 May 🌐 I can’t even go to the supermarket without being papped.