Some LGLOs use the term "interest group" to refer to ladies/men who are potential prospective members...but not yet officially part of the new membership process. The term can also be used to identify a group of women/men who are in the process of founding a new chapter.
Anon.20: I would do lots of research on the sorority you are interested in. For one thing, I am not sure I would trust the comments of someone who would be so "open" about his own process. Had you taken his comments (be they the truth or just an exageration on his part because some people think it's "cool" to talk about how "hard" their process was) to university officials, his organization would probably be in major trouble.
Find out about the sorority's position on hazing. You can contact a national officer if you want to ask questions about the policy. I wouldn't rely too much on what you hear around campus.
Good luck to you!
Edited to Add: It's a good idea to make sure you are using the correct terminology for the organization you are interested in. Many of us do not use the term "rush," but some do.