X-rating is a term used to describe movies that are considered inappropriate for younger audiences due to explicit sexual content or graphic violence. Some synonyms for X-rating include NC-17, 18+, R-18, and adults-only. NC-17 stands for "No Children Under 17" and is used by the Motion Picture Association of America (MPAA) to indicate a film with explicit adult content. 18+ and R-18 are similar labels used internationally to indicate adult-oriented content. Adults-only is a broader term used to indicate films, books, or other media that are not suitable for children due to adult themes.