By definition, public sex is sexual activity that takes place in a public context.   That means any person, or persons, performing sexual acts in public places or in private places that are still available to be viewed from public places.   Think a bedroom with the curtains open.  If you can be seen, then it’s public.   Recently, being sexually adventurous by means of public sex has gained some momentum, and was even referred to as a “craze” by the BBC that had been fueled by the internet.