A play on the name Gatsby, it's dressing up rather sexily and posting the selfie, video, or story to your social media accounts specifically to show off to an ex how sexy you still are, or to show a new romantic interest how beautiful you are. Either way a “Gatsby” post is meant to attract one hard-to-get person.

Historical perspective: In 2018 Gatsbying was considered the online dating trend. It is called Gatsbying because of what the character Jay Gatsby did in The Great Gatsby. Since it was 1922 and he didn't have access to Instagram or Snapchat, instead he devoted all of his time and attention to throwing elaborate parties to get his longtime crush, Daisy, to notice him and like him back.
See also : selfie  receipt porn  viral  LOML  RTBS  
NetLingo Classification: Online Jargon