A pump action shotgun is a shotgun with a magazine, usually a tube under the barrel. Between each shot, the shooter must move the foregrip backwards (to eject the empty shell from the chamber) and forwards (to insert a shell into the gun's chamber and close the bolt) -- the operator pumps the mechanism, thus the name pump action.

The magazine usually holds 3 - 5 shells, but most shotgun makers also sell extension kits so you can load more shells into the magazine. Many countries don't allow shotguns capable of carrying more than 2 shells in the magazine, so one has to insert a blank or filler shell into the magazine so that no more than 2 shells can be inserted.

The pump action shotgun is a durable construction which eats heavy loads and takes a beating.

The sound produced by pumping the foregrip should make any intruder wet their pants.

One of the the most famous pump action shotguns might be the Remington 870 Express.