The term 'prohibited activity' can be summarized by two crossword solutions: 'TABOO' and 'nono'. TABOO is a term used to describe an activity or behavior that is socially unacceptable or forbidden. It is often associated with religious or cultural beliefs and practices. Nono is a term used to describe something that is not allowed or prohibited. It is usually used to refer to activities or behaviors that are considered to be wrong or dangerous. Both terms refer to activities or behaviors that are not allowed or prohibited.