laser gun 
noun
1A handheld device incorporating a laser beam, used for reading a barcode or for determining the distance or speed of an object.This laser gun is the latest hand-held speed detection equipment and does not need a vehicle so it is very easy to deploy....
- These pulses reflect back to the laser gun, which calculates how much the distance is changing with time. That calculation results in a speed read-out on the laser gun.
- The advertisement used a picture of a policeman holding a speed laser gun.
2(In science fiction) a weapon that uses a powerful laser beam.There were no flaws to his game, for the most part he found the fairways with the accuracy of a laser gun and peppered the flags with some exquisite approach work....
- The firearms are big, meaty ballistic weapons - no futuristic laser guns here.
- They were all wearing black trench coats and carrying laser guns, big huge things that could blow a hole through the wall easily.