This stands for "Blu-ray Rip." It means the file was encoded from a source that was already a "release" (likely a BDRip), rather than directly from the original Blu-ray disc.
: The "Mo" could refer to a person or entity claiming exclusivity over the content, or it might imply a 'movie-only' or special 'exclusive' edition. sinister2012720pbrriphindidualaudio mo exclusive