The smell that's left inside a bathroom after someone else has taken a poop. This is an unpleasant smell (unless you like other people's poop smells), and definitely not a smell you'd like to shower in.
Roommate #1: Did you just go poop in there?
Roommate #2: Yeah, man. Just had a huge cup of coffee and had to go!
Roommate #1: Alright, I'll use the upstairs bathroom. I don't want to shower in your afterpoop.