Definitions include: Expression of disappointment, similar to 'bummer', though more forceful. 'Bummer' tends to be used when something unforeseen and unfortunate occurs. 'Rats', on the other hand tends to be used when you have been making a concerted effort to do something and it suddenly fails. You only use 'rats' about your own misfortune. You can use 'bummer' sympathetically also about someone else's misfortune.
Definitions include: The fanbase, and accepted affiliates, of the band Slipknot that grew large enough to be classified as a gang, then coninued to grow until it became classified as its own nation within all the nations of the world.