One of the most useful words to ever be invented in the English language, though it's origins are shrouded in mystery. A more sophisticated and posh version of "brah" though the meanings are similar. Can be used to express almost every emotion known to man from anger and sadness to happiness and even ecstasy.
Friend 1: How was that girl you took home last night bruh?
Friend 2: The sex was awesome but when I came i shouted BRUUUHH at the top of my lungs!
Friend 1: Bruh
Friend 1: I ate all your pizza rolls when I was drunk last night.
Friend 2: BRUH!
Friend 1: How did you do on the test bruh?
Friend 2: Totally aced it bruh, got an A plus!
Friend 1: Bruh! *Congratulatory bro-fist*