Merriam-Webster's Collegiate® Dictionary, 11th Edition
RIOT
I. noun
Etymology: Middle English, from Anglo-French riote rash action, noise, disorder
Date: 13th century
1. archaic profligate behavior ; debauchery , unrestrained revelry, noise, uproar, or disturbance made by revelers,
2. public violence, tumult, or disorder, a violent public disorder, a random or disorderly profusion , one that is wildly amusing ,
II. intransitive verb
Date: 14th century
to indulge in revelry or wantonness, to create or engage in a riot, rioter noun