Stands for "Take the loss". Frequently used to describe flunking a test, being dumped, being stood up, being beaten up or robbed, or losing one's money in the stock market, gambling, or through exploitative business schemes.
Bruh 1: Yo Bruh, we taking no L's at the club tonight.
Bruh 2: Yea Take No L's, we not getting stood up.
Bruh 1: And we gon turn up... Straight Savages