a totally douchey way of saying jack in the box, sometimes that "x" sound in "box" is too hard for people to pronounce, so they just go with the least funny alternative.
Jack: Hey Jill, Let's go to Jack in the Crack
Jill: What, are you retarded? It's Jack in the Box, that's the name of the eating establishment, and if you respect them or enjoy their food in the least bit you could refer to them by their actual name, or at least a more respectable, less douchey alternative. Dumbass.
Jack: I am sorry. I will never say Jack in the Crack again.