A slang term for the schedule 4 benzodiazepine, Klonopin. It is sought after for its euphoric effects similar to having smoked weed and drinking a few beers. Its effects can last for up to 40 hours, so it will keep you crunk all weekend if you want. At high doses (+1mg) it causes severe anterograde amnesia and ataxia.
My friend has anxiety problems and was prescribed K pins which he sold me for $10/pill. It's like burnin' a g of KB and taking a few shots, good shit.