Wiktionary
n. A bar mounted on the roof of a vehicle, such as a police car, with rotating beacons or other lights to provide a visual warning.
Usage examples of "lightbar".
The lightbar, when its interior was broken so that the chemicals might mix, would give him more than enough illumination without heat so that whatever the mages had that might sense heat in the inner vaults would not give him away.
The lightbar shivered in his hold, illumination spraying over the thing erratically, making it difficult to know what he was looking at.
He threw the cruiser into park and, more out of habit than necessity, snapped on the lightbar flashers.
Her eyes had wandered across the carpeted ceiling and extruded white plastic lightbars, but now her gaze returned to the poster for lack of anywhere better to focus.