The powdery substance made up of THC crystals from the bud of cannabis. It's basically the Cheetos dust that gets left behind on your fingers after finishing a bag of chips, but in this case, with weed.
1: Look at all the keef I collected in my grinder!
2: All mine got stuck on my fingers from piecingthe buds.
Brian: I know you want to be a Keefe, but that's only a dream. Sometimes you just got to let some dreams go.
Kevin: Shut up Brian, you're just jealous that I'm getting closer to becoming a Keefe.