1. an English statute of 1715 providing that if 12 or more persons assemble unlawfully and riotously, to the disturbance of the public peace, and refuse to disperse upon proclamation they shall be considered guilty of felony.
2. read (someone) the riot act ,
a. to reprimand; censure: The principal read them the riot act for their behavior at the assembly.
b. to give (someone) a sharp warning.