When a man is confronted with a piss trough (or communal urinal) upon entering the men's bathroom, this is the set of rules applied when urinating next to another man. In essence, as in the movie, crossing streams is forbidden.
"My buddies and I were getting thrashed at the local pub when I needed to take a piss. When I walked into the bathroom, I saw a piss trough mounted to the wall with another drunk a-hole pissin' the night away. After a quick glance, an unspoken agreement confirmed that the Ghostbuster Rules were in effect."
Pajama casual is a term used when working from home and preparing for a video conference. All business above the waist and your pajama pants down below.