The smallest sprocket of the three attached to the pedals of a typical mountain bike. So called because of its widespread use by the cycling chav- possibly because of its lack of understanding of the gear shift mechanism coupled to a total lack of physical fitness. The effect is that the chav invariably spins its legs wildly whilst making little forward progress.
Chavs invariably use in combination with a bike that's way too small and a saddle that's way too low. Supplementary effect noticed by onlookers is that the chav's knees rise to around ear level when pedalling.
If the chav's bike is a brand known to cycling aficionados, it will be nicked. If its a cheap chain-store brand it will be nicked too.
Cyclist 1 "That hill was way steep, I'm shattered"
Cyclist 2 "Me too, I was stuck on the Chav Ring all the way to the top"