noun
revolving light; flashing light; emergency vehicle light
Refers to the rotating or flashing warning lights mounted on emergency vehicles, construction equipment, or security installations.
パトカーの回転灯が赤く光っていた。
The police car's revolving lights were flashing red.
工事現場の入り口に回転灯が
A revolving warning light is installed at the entrance of the construction site.
A broader term for warning lights, which may include flashing LED arrays, not necessarily revolving. 回転灯 specifically implies a rotating mechanism.
Compound of 回転 (rotation) and 灯 (light), literally 'rotating light'.