I think he’s given Accoster a nickname of sorts...”You are fake news.”
[34 second clip, first news conference as President Elect, January 11, 2017]
https://www.youtube.com/watch?v=Vqpzk-qGxMU
Trump to Accoster: “...I like real news, not fake news. You’re fake news.”
[36 second clip after press conference, August 14, 2017]
https://www.youtube.com/watch?v=_BIqpQ7i1iI