Definition of happy slapper in English:

happy slapper

noun

British
informal
  • See happy slapping

    • ‘People were drawn in as random victims, with "happy slappers" seeing it as a way to fame and notoriety.’
    • ‘Tube and mainline rail passengers around London have reported unprovoked 'happy slapper’ attacks.’
    • ‘There have been several arrests of happy slappers, and police in Germany and Switzerland say the trend has become such a problem they have contacted their UK counterparts to get advice on tackling the craze.’
    • ‘If you're a happy slapper, you're manufacturing evidence against yourself.’
    • ‘One teenager said "happy slappers" were attempting to outdo one another by recording more serious attacks.’