It's a insult used on a person who is a pain or useless. The insult reffers to when a male ejaculates on his pants and a stain is left where the semen (or in slang cum fell. Hence the use of "cum") . It's acronym form is CSOTPOS. Used by many teenagers and is not understood by most teaches so it is higly useful.
An insulting term that compares someone to the stains left in a man's underwear by his dick. An obnoxious, digusting person that you can't stand to be around.
My bossmade me work overtime every night this week. What a dick stain!
When the vibe/mood/aura of a room/place seems uneasy and out of the ordinary, the air is heavy and something feels wrong. It commonly foreshadows that something terrible is about to happen.
The term was heavily popularized in 2017 when the game DDLC (Doki Doki Literature Club) was released, and one of the characters (Yuri) uses it.
“Stagnating air is common foreshadowing that something terrible is about to happen” -Yuri 2017