Wiktionary
tweetheart
n. 1 (context Internet slang English) A http://en.wikipedia.org/wiki/Twitter user who is popular with others. 2 (context Internet slang English) A http://en.wikipedia.org/wiki/Twitter user who is one's personal friend or within one's broader social networking circle. 3 (context Internet slang English) A http://en.wikipedia.org/wiki/Twitter user with whom one is infatuated or involved romantically, especially if they were first met through the service.