BESL Share definition Flag means "broken english as a second language". Applies to a person when their English is utterly incomprehensible, even if it's not their first language. I can't understand a word Rami is saying. He must have failed his BESL class. BESL by Hordak March 1, 2008 0 0 Get merch Get the BESL mug. Buy Now — $32.95 See more merch