tweetup (?twi?t??p) n (Communications & Information) slang a meeting at which people who communicate with each other via the social networking site Twitter meet face to face [C21: a blend of tweet and meetup, an instance of people meeting face to face, from meet1]Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014