Riot  —n. 1 a violent disturbance by a crowd of people. B (attrib.) Involved in suppressing riots (riot police). 2 loud uncontrolled revelry. 3 (foll. By of) lavish display or sensation (riot of colour and sound). 4 colloq. Very amusing thing or person. —v. Make or engage in a riot.  read the riot act act firmly to suppress insubordination; give warning.