not to be confused with a bus down, which is a half smoked cigarette, a jailhouse short is a lit cigarette butt that would have been discarded had one not asked for it. on par with fishing butts out of an ashtray and relighting them.
comes from northeastern u.s. slang
Crackhead: "Can I get a cigarette?"
Guy: "Sorry, last one. You want this bus down?"
Crackhead: "Mothafucka, this ain't no bus down, this is a jailhouse short!"