Rioting is the violent, uncontrolled behaviour of a crowd: fighting, wrecking, burning, smashing cars or buildings. You hear it in the news: “rioting broke out,” “three nights of rioting.” It names the action or the event, not one person. It is more formal than “a big fight” and more exact than “trouble.” Though actually, a loud, angry march is not automatically rioting. The word is for when the crowd loses control and turns to violence and damage.