social networking site
n (Communications & Information) a website that allows subscribers to interact, typically by requesting that others add them to their visible list of contacts, by forming or joining sub-groups based around shared interests, or publishing content so that a specified group of subscribers can access it
Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014