A Gun

1. A device for projecting a hard object very forcefully; a firearm or cannon.
   1. A very portable, short firearm, for hand use, which fires bullets or projectiles, such as a handgun, revolver, pistol or Derringer.
   2. A less portable, long firearm, bullet- or projectile-firing; a rifle, either manual, automatic or semi-automatic; a flintlock, musket or shotgun.
   3. (military) A cannon with relatively long barrel, operating with relatively low angle of fire, and having a high muzzle velocity.^[1]
   4. (military) A cannon with a 6-inch/155mm minimum nominal bore diameter and tube length 30 calibers or more. See also: howitzer; mortar.^[1]
   5. (figuratively) A firearm or cannon used for saluting or signalling.^Wp
2. A device operated by a trigger and acting in a manner similar to a firearm.
   1. Any implement designed to fire a projectile from a tube.

air-pressure pellet gun;  air rifle;  BB gun;  zipgun;  nail gun;  a potato gun

1. 2. A device or tool that projects a substance.

a squirt gun;  a spray gun;  a grease gun

1. 3. A device or tool that applies something rather than projecting it.

a rivet gun;  a screw gun;  a price-label gun

3. (surfing) A long surfboard designed for surfing big waves (not the same as a longboard, a gun has a pointed nose and is generally a little narrower).
4. (cellular automata) A pattern that "fires" out other patterns.
5. (colloquial, metonymically) A person who carries or uses a rifle, shotgun or handgun.
6. (television) An electron gun.
7. (colloquial, usually in the plural) The biceps.
8. (nautical, in the plural) Violent blasts of wind.
9. (colloquial) An expert.
10. (Australia, slang) Someone excellent, surpassingly wonderful, or cool.