run riot

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run riot (third-person singular simple present runs riot, present participle running riot, simple past ran riot, past participle run riot)

1. (idiomatic) To act in an uncontrolled, unbridled manner.
   • 1939 September, D. S. Barrie, “The Railways of South Wales”, in Railway Magazine, page 158:

     No wonder, then, that against a background of surging aggressive prosperity, South Wales built up during the last half of the nineteenth century a local railway system of great density and complexity, in which almost every company competed with every other in its area, and in which working agreements, running powers and strategic junctions ran riot across the railway map.

   • 2024 November 13, Paul Bigland, “Much to admire... but pockets of neglect”, in RAIL, number 1022, page 48:

     All is well until Treorchy, where the platform is swamped by teenagers who have been attending an event. Around four dozen unescorted 12 to 16 year-olds swarm aboard and begin to run riot through the train. Their behaviour is appalling and the presence of CCTV no deterrent.

2. (idiomatic) To be uncontrollable.
   • 2018 February 10, Phil McNulty, “Tottenham Hotspur 1 - 0 Arsenal”, in BBC‎^[1]:

     And it was only the defiance of Cech that kept a rampant Spurs at bay in the second half, producing a collection of outstanding saves to somehow keep Arsenal in contention as Pochettino's side threatened to run riot.