Delulu is a slang term derived from the word "delusional" and is often used to describe someone who holds unrealistic or overly idealistic beliefs or fantasies. It is typically used to criticize or mock individuals who have unrealistic expectations or notions, especially in the realm of relationships, celebrity fandom, or other areas where people may have unrealistic perceptions or exaggerated fantasies. The term originated from the K-Pop fan community and was originally used to criticize other fans beliefs and theories about K-Pop celebrities. Since 2022, the term has gained popularity on social media platforms such as TikTok and is now widely used as a slang term for "delusional".