In a vast cubicle office environment, when one stands up in one's own cube and looks along the tops of the many cube walls stretching out to the horizon. The cube horizon can be interrupted by the heads of people walking around. And by many heads at once if there is a loud, unexplained noise in the area. This can result in a phenomenom called prairie-dogging: many people stand up and look around like prairie dogs coming out of their holes.

I first came across "cube horizon" in James Hynes' novel "Kings of Infinite Space."

A casual invitation / threat used by an individual that is not afraid of fucking someone up.