Hi, Dinghui! It means exciting, lively, or amusing often in a way that is slightly shocking. For example: The comedian was notorious for telling racy jokes during their television performance. Some synonyms for racy are: suggestive; immodest; off color; risqué; sexy; lewd; crude

This word usually means that media (e.g., a book, a photograph, a television show, a movie, a comedy routine, an advertisement) contains sexual themes. In other words, "racy" means that the content is intended to create sexual ideas and feelings, even if it is only in a playful way.