gitsurfing 

Gitsurfing (aka biddysurfing) is when a young person (usually around 9-15) runs up behind an old person and jumps on his or her back, the momentum of the run-up causing the oldie to move forward a few steps before falling to the floor. The craze, though possibly not the words gitsurfing or biddysurfing, is thought to have originated in Manchester in the mid-1990s and appears to be slowly growing in popularity.

I'll give you a thick ear if I hear you've been gitsurfing again.

gitsurfing by cactuscat September 15, 2006

Git Surfing 

Like carjacking or joyriding, only hijacking an unsuspecting person instead of a car. The term was invented by Chris Morris for the 'Crime' episode of Brass Eye. It was a popular pursuit in the fictional, crime-ridden estate of Coswick. The git surfer creeps up behind their victim and jumps on their back, forcing them to run around at 'terrifying leg speeds'.

They hijack pedestrians and run them around a terrifying leg speeds. It's called "git surfing", all too often, the "git" is one of their own mothers

Git Surfing by Billsz June 30, 2011