A gun is a ranged weapon designed to use a shooting tube (gun barrel) to launch projectiles. The projectiles are typically solid, but can also be pressurized liquid (e.g. in water guns/cannons, spray guns for painting or pressure washing, projected water disruptors, and technically also flamethrowers), gas (e.g. light-gas gun) or even charged particles (e.g. plasma gun). Solid projectiles may be free-flying (as with bullets and artillery shells) or tethered (as with Taser guns, spearguns and harpoon guns). A large-caliber gun is also called a cannon.
The means of projectile propulsion vary according to designs, but are traditionally effected pneumatically by a high gas pressure contained within the barrel tube, produced either through the rapid exothermic combustion of propellants (as with firearms), or by mechanical compression (as with air guns).