"Cuckstar" is a term used in the context of cuckold fetishes, which refers to a specific role-playing scenario within a sexual relationship. In this scenario, the female partner engages in sexual activities with another man while her male partner (also known as the "cuckold" or "cuck") watches or is made aware of it. The term "cuckstar" can be used to describe the male participant who engages in this activity with the cuckolded woman, effectively starring as the "hero" in this fantasy scenario.
In a broader context, it's important to remember that not all individuals who engage in cuckolding or similar fetishes necessarily identify with these labels, and that everyone's experiences and preferences within their sexual relationships should be respected. The term is primarily used for descriptive purposes in discussing the genre of porn featuring this particular role-playing scenario.