strobe light
From Longman Dictionary of Contemporary Englishstrobe lightstrobe light /ˈstrəʊb ˌlaɪt $ ˈstroʊb-/ (also strobe) noun [countable] TPEa light that flashes on and off very quickly, often used in places where you can danceExamples from the Corpusstrobe light• She was dressed in black gauze and held a strobe light aloft like a mitre.• The station's interior variable message sign and accompanying exterior strobe light have not worked since May.Origin strobe light (1900-2000) stroboscope “instrument producing quickly flashing light” ((19-21 centuries)), from Greek strobos “going around quickly” + English -scope (as in telescope)