Quick Definition: Another name for the Seduction Community.
The Secret Underground Internet Seduction Community is a term that some PUAs use to refer to the loose-knit community of men working to improve their success with women and become pickup artists. The term is not used commonly, and, when it is, it is used almost exclusively in its abbreviated form: SUISC.
Like the name suggests, the SUISC exists mainly on the Internet in the forms of secret and not-so-secret forums where men go to give and find advice on picking up women, as well as sharing their successes and failures in field reports. There are also local lairs, where guys get together to meet up and practice in the real world, as well as various pickup companies that offer bootcamps and structured coaching.
The term SUISC is often used ironically, as the once secret community has grown increasingly mainstream, with several books and TV shows on the subject, as well as a number of movies in production. The commercialization of pickup and the creation of an entire industry centered on picking up women has encouraged more PUAs to venture out of the hidden corners of internet forums and cash in on their skills with women.
Still, the SUISC maintains a fairly low profile—perhaps due to the controversial and sensitive nature of the subject matter, which has led to the creation of a distinct subculture. So the term remains somewhat appropriate.
I know a couple of guys who claim to be members of the SUISC.