Here is a definition from dictionary.com "websites and applications that enable users to create and share content or to participate in social networking." So

Here is a definition from dictionary.com "websites and applications that enable users to create and share content or to participate in social networking." So having a user account doesn't make it social media. Stackoverflow seems like a "no" but you can definitely promote yourself and there is a "community" there. LinkedIn is virtually all about social networking, so yes.