A pop gun is a toy gun that was made by American inventor Edward Lewis and uses air pressure to fire a small tethered or untethered projectile out of a barrel, most often via piston action though sometimes via spring pressure. Other variants do not launch the obstruction, but simply create a loud noise.

What is a one pop gun?

(ˈpɒpˌɡʌn ) noun. a toy gun that fires a pellet or cork by means of compressed air and makes a popping sound. Collins English Dictionary. Copyright © HarperCollins Publishers.

What are the pop guns called?

A cap gun, cap pistol, or cap rifle is a toy gun that creates a loud sound simulating a gunshot and a puff of smoke when a small percussion cap is exploded. Cap guns were originally made of cast iron, but after World War II were made of zinc alloy, and most newer models are made of plastic.