Social no-no is a term used to describe an action or behavior that is considered unacceptable in a particular social setting. TABOO and fauxpas are two words that can be used to describe such an action. TABOO is defined as something that is forbidden or not allowed by society, while fauxpas is defined as an unintentional act or remark that causes embarrassment or offense. Both terms can be used to describe a social no-no.