A specific type of ghost in a chatroom or other communication service who appears yet present, while in fact already gone, as a result or side effect of a host error. Many services offer a command to erase them from the list of people present as well as other type of ghosts, such as NickServ's /ns ghost.
When someone farts in public areas assuming they are alone, and out of nowhere another person appears and walks into your toxic cloud. Just stand back and warn them of a Hostile Ghost in the area!
The act of posting a thought/question/comment and not waiting around to see the replies/answers/reactions. This can be either an intentional act , esp with inflammatory/controversial/provocative posts , or unintentional where the OP simply forgets about it , ie due to neurodivergence.
When Sheila asked Jane for a restaurantrecommendation, Jane rolled her eyes and said "OMG Sheila didn't you ghostpost this last week!