A term commonly used amongst recreational drug users to describe an extremely potent form of the tranquiliser ketamine. The effects of large intakes of this substance can range anywhere from a desire to listen to extended periods of fleetwood mac, sitting around in cardboard boxes, and inevitably, getting lost in the k-hole. Watching people partake of Bulletproof Ket is, prehaps not unsurprisingly, a great deal of fun.
Did you see Nik after his third line of that Bulletproof Ket? I've never seen someone having it out with an imaginery bathroom dwarf before.