A shit that you spend a nice long time working on, but then when you're done, isn't in the toilet! You could have sworn you took that shit but it's gone! You wipe your arse and it's perfectly clean. Where did the shit go? I don't know!
The feeling you get when you urgently need to take a major shit. Get to the toilet, sit down but nothing comes out. Maybe a small fart or the smallest turd crumb. Leaves you scratching your head after. Makes you think your last consumed food or beverage was a poor choice.
I got stuck in traffic and felt like I needed a shit. I rushed back to my house and run to the toilet. I sat there for a half hour but no shit came out. Fucking ghost shit!
When you shit and whipe your ass and its clean. *then you look in the toilet, the shit went down the hole, thus simulating the effect that your shit never existed.
*the first condition is enough to constitute a ghost shit.