Similar to bail, flake, ditch, or escape
1) To show up or make an appearance, but then leave suddenly and/or hastily without notice.
Similar to a 'flake,' but differs in that the person almost follows though only to ditch/bail shortly after. Generally associated with unreliable persons.
2) To leave hastily, generally without notice.
"Dude, what happened to you yesterday? You totally ghosted out."
Tech 2: Calm down man, I ghosted the primary hard drive yesterday so I have a backup.
In MMO's or shooter games, when playing a rogue or ninja type class or in shooters, you snipe, knife, or do a takedown, you sneak up and burn down a player right behind the victim's group and they didn't even notice.