rogue
n.n. behaving in a way that is different from what is normal or expected, often causing trouble. You use this to describe someone or something that stops following the rules of a group.
n. behaving in an erratic or dangerous fashion by operating outside established norms or controls. Often used to describe an individual who acts independently of their organization or a system that malfunctions unpredictably.
A rogue wave hit the ship without any warning.
The agency spent months trying to track down the rogue agent who had stolen the secret files.
In the absence of central oversight, several rogue states began developing prohibited technologies, effectively undermining the international treaty designed to ensure global security.
Uncertain. From either: * Earlier English roger (“a begging vagabond who pretends to be a poor scholar from Oxford or Cambridge”), possibly from Latin rogō (“I ask”). * Middle French rogue (“arrogant, haughty”), from Old Northern French rogre (“aggressive”), from Old Norse hrokr (“excess, exuberance”), for which see Icelandic hroki (“arrogance”), though OED does not document this. * Celtic; see Breton rog (“haughty”).
Commonly used as an attributive adjective before a noun; frequently collocates with 'agent', 'state', or 'element'.