Taboos are actions performed by an individual that are not accepted by their larger society. These are things that go against cultural norms, and those norms will often be reinforced by members of that culture. Indulging in taboo may cause a person to be discriminated against or have them labeled as a pariah. In American business culture, for example, it is considered impolite, or taboo to talk about money and income. If you talk about your wages at work you could be shunned or even reprimanded, while in many other countries this taboo is not true.
In my personal experience my appearance has been somewhat of a taboo to certain portions of the American population. I will occasionally be confronted by older, or more conservative people and told that my tattoo or my piercings are grotesque, or just done for attention. However in other portions of the population such as millenials and liberal people, it is instead taboo to confront someone about their body modifications.