Slapping a random person (they can be on the bus, walking down the street, whatever) whilst recording the act with a video camera phone. It's a very unfortunate London phenomenon. Attackers are usually yoots (ghetto versions of chavs) thinking they are rudeboys. Victims are usually boys around the same age as the attackers, but it's not unknown for victims to be older, or even women. Sometimes the tables are turned, as there are videos going around where the attacker is happy slapped by the victim. More power to the victims, I say. The act is totally random, so be on the lookout for a group of pussified yoots pointing their camera phone (that their mum bought) at you.
If you get happy slapped, grab the camera phone and smash it on the ground.
There is, however, a reversal but u gotta get your timin right (u can see wen its gonna happen cos a chav will be walkin fairly quickly to you and close by someone will have a fone out aimin roughly in ur direction. when he brings his hand up hes vulnerable, and then you slap him, AS HARD AS POSSIBLE!!! then run off give em the finger if you want just to add effect
(3 times out of four ive pulled this one)
The victim is almost always totally unaware, and they use it to their advantage so the vicim doesn't have a chance to grab the slapper and beat the living shit out of them.