gun

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A weapon consisting of a metal tube from which a projectile is fired at high velocity into a relatively flat trajectory, especially.
• noun A portable firearm, such as a rifle or revolver.
• noun A cannon with a long barrel and a relatively low angle of fire.
• noun A device resembling a firearm or cannon, as in its ability to project something, such as grease or paint, under pressure or at great speed.
• noun A discharge of a firearm or cannon as a signal or salute.
• noun One who is armed with or skilled in the use of a gun.
• noun The throttle of an engine, as of an automobile.
• noun Slang The biceps muscles of the arms.
• intransitive verb To shoot (a person).
• intransitive verb To open the throttle of (an engine) so as to accelerate.
• intransitive verb To hunt with a gun.
• idiom (go great guns) To proceed or perform with great speed, skill, or success.
• idiom (hold a gun to (someone's) head) To put pressure on someone.
• idiom (under the gun) Under great pressure or under threat.

from The Century Dictionary.

• To shoot with a gun; practise shooting, especially the smaller kinds of game.
• Past participle of gin.
• noun A military engine of the mangonel or catapult kind, used for throwing stones.
• noun A metallic tube or tubular barrel, with its stock or carriage and attachments, from which missiles are thrown, as by the explosive force of gunpowder or other explosive placed behind them at the closed end of the tube, and ignited through a small hole or vent; in general, any firearm except the pistol and the mortar.
• noun Specifically, a comparatively long cannon used for obtaining high velocities with low trajectories, as distinguished from a howitzer or a mortar.
• noun In hunting, one who carries a gun; a member of a shooting-party.
• noun A tall cylindrical jug in use in the north of England.
• noun In plate glass manufacturing, a device for fixing the breadth of the plate.
• noun Its principal peculiarities are the unbroken smoothness of its surface and the relation of its thickness at all points (determined by experiment) to the pressure in firing. Of all large smooth-bore guns, it is, not excepting the 15-inch Rodman gun, the most easily handled. The Dahlgren and Rodman 15-inch guns are equal as to accuracy and efficiency.
• noun A person of distinction or importance: more commonly called a big gun.
• noun A single-loading small-arm, caliber 0”.408, used in the Italian army.
• noun A magazine bolt-gun used in the Italian and Swiss armies.
• In forestry, to aim (a tree) in felling it.
• noun A professional criminal; a thief; a pickpocket.

from the GNU version of the Collaborative International Dictionary of English.

• noun A weapon which throws or propels a missile to a distance; any firearm or instrument for throwing projectiles, consisting of a tube or barrel closed at one end, in which the projectile is placed, with an explosive charge (such as guncotton or gunpowder) behind, which is ignited by various means. Pistols, rifles, carbines, muskets, and fowling pieces are smaller guns, for hand use, and are called small arms. Larger guns are called cannon, ordnance, fieldpieces, carronades, howitzers, etc. See these terms in the Vocabulary.
• noun (Mil.) A piece of heavy ordnance; in a restricted sense, a cannon.
• noun (Naut.) Violent blasts of wind.
• noun a wrought iron breech-loading cannon named after its English inventor, Sir William Armstrong.
• noun a person superior in any way.
• noun the barrel or tube of a gun.
• noun the carriage on which a gun is mounted or moved.
• noun (Chem.) a general name for a series of explosive nitric ethers of cellulose, obtained by steeping cotton in nitric and sulphuric acids. Although there are formed substances containing nitric acid radicals, yet the results exactly resemble ordinary cotton in appearance. It burns without ash, with explosion if confined, but quietly and harmlessly if free and open, and in small quantity. Specifically, the lower nitrates of cellulose which are insoluble in ether and alcohol in distinction from the highest (pyroxylin) which is soluble. See Pyroxylin, and cf. Xyloidin. The gun cottons are used for blasting and somewhat in gunnery: for making celluloid when compounded with camphor; and the soluble variety (pyroxylin) for making collodion. See Celluloid, and Collodion. Gun cotton is frequenty but improperly called nitrocellulose. It is not a nitro compound, but an ester of nitric acid.
• noun See under Deck.
• noun the time at which the morning or the evening gun is fired.
• noun a bronze, ordinarily composed of nine parts of copper and one of tin, used for cannon, etc. The name is also given to certain strong mixtures of cast iron.
• noun (Naut.) an opening in a ship through which a cannon's muzzle is run out for firing.
• noun (Naut.) the blocks and pulleys affixed to the side of a ship, by which a gun carriage is run to and from the gun port.
• noun (Naut.) a tackle composed of two single blocks and a fall.
• noun a wrought steel breech-loading cannon, named after its German inventor, Herr Krupp.
• noun a breech-loading gun or a group of such guns, mounted on a carriage or other holder, and having a reservoir containing cartridges which are loaded into the gun or guns and fired in rapid succession. In earlier models, such as the Gatling gun, the cartridges were loaded by machinery operated by turning a crank. In modern versions the loading of cartidges is accomplished by levers operated by the recoil of the explosion driving the bullet, or by the pressure of gas within the barrel. Several hundred shots can be fired in a minute by such weapons, with accurate aim. The Gatling gun, Gardner gun, Hotchkiss gun, and Nordenfelt gun, named for their inventors, and the French mitrailleuse, are machine guns.
• noun (Naut.) to blow a gale. See Gun, n., 3.
• intransitive verb To practice fowling or hunting small game; -- chiefly in participial form.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A very portable, short firearm, for hand use, which fires bullets or projectiles, such as a handgun, revolver, pistol, or Derringer.