Is Reddit social media?
Social media is a phenomenon so large as to have a myriad different definitions. Therefore, answering a question whether anything is considered a social media platform will depend on the definition you're using.
At its core, Reddit is a place for people to create, distribute, and share content, ideas, experiences, and other information. Therefore, Reddit is a social media platform. Unlike, for example, Facebook, it is based around forum-like, independent and anonymous communities versus individual users.