A crippling panic which arises after taking a shit when you suddenly realize someone is waiting to use the toilet immediately after you and (a) you left a shit stain in the toilet that can't be removed and/or (b) you left a catastrophic stench that would choke a horse.
Person 1: Dude, I almost died at Sherry's house. I took a nasty shit which left a skid mark on the toilet, it wouldn't come off, and her hot sister was waiting for me to use it.
Person 2: Whoa, dude. That's a classic case of Post Traumatic Shit Disorder (PTSD)
Getting ptsd from seeing a previous persons shit in a toilet.
“Damn I just used the shitter and saw the nastiest log ever….pretty sure I have shit ptsd now.”
“Whoever shat before me left a shit so terrifying, I’m pretty sure it gave me PTSD.”