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Gun is also used as an adjective which refers to someone with extreme talent. This usage of gun started on the popular british comedy, 'Dads Army'. It was when Private Godfrey refered to training soldier Bluey, played by Matthew Charalambous of South Australia, to be a 'gun' shooter. Since then whenever people use the common saying, they think of a true gun, Matthew Charamlambous.
A gun is a common name given to an object that fires high-velocity projectiles. The projectile is fired through a hollow tube known as the gun's barrel. The projectile's caliber, or diameter, is usually designated in fractions of an inch or in millimeters. Differing from the musket, most modern guns are rifled, with a series of grooves spiraling along the barrel; exceptions include smoothbores on tanks, AFVs and some artillery.
The term gun is often used synonymously with firearm, but this is common only for civilian usage. In military usage, the term refers only to artillery that fires projectiles at high velocity, such as naval guns (which are never referred to as cannon) or tank guns. A gunner is a member of the team charged with the task of operating and firing a gun. By military terms, mortars and all hand-held firearms are excluded from the definition of guns. Two exceptions to this are the shotgun - which is hand-held, has a smooth bore and fires a load of shot or a single projectile known as a slug - and the machine gun - which is a fully-automatic weapon mounted on a tripod or bipod and almost always operated by a crew.
The word gun is also applied to some more or less vaguely gun-like or gun-shaped tools, such as staple guns and glue guns.
