A day off from classes or school due to a perceived criminal and dangerous event. The irony is that in a ghetto these events would be quite common, so instead of being a scary emergency situation, they are more on par with an unexpected snow day, and are in fact quite harmless. Examples include nearby robberies or murders, escaped convicts, bomb threats, and prank fire alarms.
We had a ghetto snow day last week because someone robbed a check cashing store and was spotted on campus. Although we were notified about this a couple hours late, we still had no classes!