Normally a Thursday night. It's not quite the weekend, but after working 4 days you need to go out and have a beer or twelve. Can involve trivia, live music, watching basketball/baseball/football or karaoke.
"At trivia last Cato got pre-weekend wasted."
"Ugh, it's almost Friday and I'm so ready for the weekend. Let's go out tonight and get pre-weekend wasted!!"