Comment by krisoft

For funsies i would call it a “vessel not under command”. At least after the breakup that feels to fit.

But for real, i think the simple answer is that debris falling from space is outside of the scope of the ColRegs. Simply speaking they come too fast so you can’t maneuver your vessel out of their way, and unless you are a warship you don’t have the tools to even know where exactly they will hit. If you try to run you might even put yourself in their path. After all from the most unlucky position they would be just bright stationary spots on the sky getting ever so slightly bigger. Until they start to get bigger faster and faster. (Constant bearing and decreasing range being the hallmarks of an impending colision.)