A WildCat! BBS is one that ran on Mustang Software's WildCat! platform.
Mustang's package became the most popular around; it was frequently updated, affordable and very easy to set up. It also made it incredibly easy to become a point on FidoNet. I can't think of a single BBS that didn't use it in the mid-nineties, aside from the niche Mac boards.
I used it to run a BBS for a year in 1995, and was pleased with the level of control I had over my users. (In some ways it was a much more satisfying experience than running a Web site.) The only snag was that really it required a separate ANSI screen editor to generate the menus.
These days, WildCat! is still around, and is produced by Santronics Software; it now runs as a Web server and telnet server as well as, of course, allowing people to dial up directly. Mustang software, however, have gone down the tubes.