An acronym that stands for "Man, Come on Bruh" or, as it's often pronounced, "MEH COME OWN BRUH."
An exclamation of disbelief or skepticism.
It is acceptable for "bruh" to be substituted with "brah" or "bro," however the original and most widely accepted use is "bruh."
Emailing the entire class the night before the final exam for notes? MCOB.