A diversionary pastime in which teenage boys throw open jack-knives at the ground in an attempt to hit it and, in doing so, express their inarticulate rage and passion towards the world. Often referred to as a "game" similar in approach to darts or horseshoes, it is more accurately an outlet for troubled adolescent angst, and what rules exist are apocryphal and contradictory at best. (see: Calvinball)