A blackade is a very large crowd of black girls and/or guys blocking a hallway in school or any other place. It can be very annoying at times when trying to get to somewhere in a hurry, especially when they start yelling at you for no other reason than getting knocked over by themselves.
Bob: Man, I really have to get to math class. O crap Its a blackade!
To be obstructed from movement at normal speed by the presence of slow-moving African Americans intent on monopolizing the entire sidewalk, escalator, hallway, etc...