A semi-formal dance for which girls get far too dressed up (gowns and fancy jewelry, etc.) and for which many guys come severely under-dressed. Humiliating, yes. Enjoyable, perhaps if you come drunk.
"Dude, did you see that girl's dress at cotillion? she swears she's at a prom?"
"Yeah man, all I wore was some khaki's and my dad's dress shirt."
When finance content creators rent out fancy cars and flexcash to seem richer than they really are in order to promote and sell their “get rich quick” courses.
The use of the word "blue" to refer to sexually explicit content was first recorded in Scotland in 1824. "Blue" meant "lewd" because prostitutes dressed in blue gowns.