Affray is a somewhat old-fashioned word for an assault or public disturbance. A sports fan disappointed in their favorite team's loss might start an affray in the street after the game.
This dated legal term isn't used much in the U.S. these days. Imagine soccer fans rioting in the streets after a game, or a rowdy bar fight involving many people. If these events are frightening to onlookers, they're considered an affray. In Britain, you can be charged with affray if you participate in this kind of group violence. Affray, via the Old French affrai, "disturbance," comes from a Latin root meaning "to take out of peace."