Baltajia, plural of baltaji, also baltaguia, in its Egyptian intonation. The word was made popular in the Arab protests of 2011 in Tunisia and Egypt. It is thought to be of Turkish origin, meaning "weapon wielding thug".
Baltajia has come to reference any group of rubble rousing individuals that infiltrate an otherwise peaceful protest for sabotaging or other more menial purposes. The baltajia can either be for hire for political aims, or just plain street thugs whose only goal is to loot and plunder.
There was a first wave of peaceful and thoughtful protesters which was then followed by a stone wielding horde of baltajia. That was the time when all hell broke loose.