How do I classify a website that is similar to a blog or forum but doesn't fit those options exactly, such as a wiki site? [1]
Use the "Website" tag. That tag is appropriate for all websites that do not fit any of the narrower definitions above.
Links
[1] https://www.dmlp.org/faq/how-do-i-classify-website-similar-blog-or-forum-doesnt-fit-those-options-exactly-such-wiki-site