Wiktionary
n. A hand-held (or mounted) device that emits a radar beam and uses the Doppler effect to measure the velocity of moving objects (especially traffic)
Wikipedia
A radar speed gun (also radar gun and speed gun) is a device used to measure the speed of moving objects. It is used in law-enforcement to measure the speed of moving vehicles and is often used in professional spectator sport, for things such as the measurement of bowling speeds in cricket, speed of pitched baseballs, athletes and tennis serves.
A radar speed gun is a Doppler radar unit that may be hand-held, vehicle-mounted or static. It measures the speed of the objects at which it is pointed by detecting a change in frequency of the returned radar signal caused by the Doppler effect, whereby the frequency of the returned signal is increased in proportion to the object's speed of approach if the object is approaching, and lowered if the object is receding. Such devices are frequently used for speed limit enforcement, although more modern LIDAR speed gun instruments, which use pulsed laser light instead of radar, began to replace radar guns during the first decade of the twenty-first century, because of limitations associated with small radar systems.
Usage examples of "radar gun".
The trooper had his car just behind a small crest, which allowed cars heading up to Pennsylvania to fly by, right past his radar gun before they knew it.
She keeps the car under fifty for the next mile, knowing she is still in range of the automated system's radar gun.
A police cruiser sat on the side of the road, a radar gun perched on the door.
She grabbed a radar gun, aimed, squinted at the reading, put it aside and took an ionoscope.
I'm going to go run a speed trap the rest of the night, until I get so tired I can't read the numbers on the radar gun anymore.
The equipment was the usual nondescript mess of electronics which one meets in any lab: it might have been a mock-up of a new computer, a radar gun-sight, a traffic control system, or a ham radio.
Today, Sunday, as a black Lexus SUV passed this jog in the road the radar gun on Lucy Kerr' s dashboard registered a legal 44.
Mel got back in the Mercedes and drove carefully out of town, accompanied by Harold and his radar gun.