early 13c., "debauchery, extravagance, wanton living," from O.Fr. riote (masc. riot) "dispute, quarrel," perhaps from Prov. riota, of uncertain origin. Meaning "public disturbance" is first recorded 1390. Meaning "something spectacularly successful" first recorded 1909 in theater slang. The verb is attested from late 14c. Run riot is first recorded 1520s, a metaphoric extension from M.E. meaning in ref. to hounds following the wrong scent. The Riot Act, part of which must be read to a mob before active measures can be taken, was passed 1714 (1 Geo. I, st.2, c.5). Riot girl and alternative form riot grrl first recorded 1992.