happy slapping n (Law) informal Brit the practice of attacking, esp slapping, an unsuspecting passer-by and filming it with a mobile camera phone, footage of which is then circulated for the amusement of others [C21]Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014