A broad category or genre of communications media which occasion or enable social interaction among groups of people, whether they are known to each other or strangers, localized in the same place or geographically dispersed. It includes new media such as news groups, MMOGs, and social networking sites. Such media can be thought of metaphorically as virtual meeting places which function to occasion the exchange of media content among users who are both consumers and producers. Social media have also become adopted as a significant marketing tool.
Chandler, Daniel–Munday, Rod (2011): A Dictionary of Media and Communication. Oxford University Press. Oxford. p. 397. See the Online Edition