back jump
n.— «One way of getting to tag trains was a method called doing a “back jump.” This when you hide near a station or lay up, wait til a train pulls in, then quickly do as much painting as you can before the train rolls out again. It’s quite dangerous as it in- volves crossing tracks and being around moving trains. There was a kid killed last year at Acton doing this sort of thing.» —“Blood on the tracks” by Esther Addley Guardian (United Kingdom) Jan. 20, 2007. (source: Double-Tongued Dictionary)