n. A 1%er motorcycle gang and organized crime syndicate whose headquarters is located in SoCal, originally formed in 1969 by Hispanic Vietnam War veterans who had been denied entry into Hell's Angels due to their race. They are notorious for some of their criminal activity, including drug dealing (esp. methamphetamine), money laundering, robbery, extortion, illegal possession of firearms, and murder. Ask anyone who knows motorcycle gangs well, and they will probably tell you that the Mongols are one of the most notorious and badass motorcycle gangs in the world.
Biker Dude: I'm gonna get initiated into the Mongols, cuz I'm a badass motherfucker.
Friend: I'd like to see you try!