AEG - Automatic Electric Gun - An Airsoft gun that uses a battery-powered electric motor to drive a piston which compresses the air that propels the pellet.

AK (47, 74, etc.) - Avtomat Klashnikova, or Automatic Kalashnikov. The most widely used automatic rifle line in the world, Russian-designed; there are several Airsoft variants.

AUG - Armee Universal Gewehr, or Army Universal Gun. A modern bullpup rifle made by Steyr of Austria and used by several countries' military forces.

Bullpup - A rifle design that places the receiver and magazine of the weapon behind the grip and trigger rather than in front, which makes the weapon more compact while keeping a normal barrel length to maintain accuracy.

CAWS - Close Assault Weapons System - a program started by the US military to encourage the design of extremely lethal close-range weapons systems such as full-auto shotguns. The most notable product of this program was H&Ks CAWS which is a full-auto 12 gauge bullpup shotgun.

CQB - Close Quarters Battle. The general term to describe any firearms combat in physically restrictive surroundings, such as inside buildings. Typically CQB engagements will happen at less than fifteen yards. Usually much less.

FAST Company - Fleet Anti-terrorism Security Team. An elite unit of the USMC that specializes in CQB methods and anti-terrorist tactics.

GBB - Gas Blow-Back. This term describes gas powered Airsoft guns that utilize a charge not only to fire the BB but to cycle the action so as to mimic the operation of a real firearm.

H&K - Heckler & Koch, a German firearms manufacturing firm that produces reliable and accurate handguns (like the P7, USP, Mk23 SOCOM), submachine guns (like the MP5 series and the MC51), and rifles (such as the G3 series), on which a number of popular Airsofts are based.

Hop-Up - Usually a rubber patch at the top of an Airsoft gun's chamber that causes friction on a BB and thus imparts a backspin as it's fired. This provides for better accuracy and a straighter trajectory on the BB.

HRT - Hostage Rescue Team. This is the FBI's elite counter terrorist SWAT unit based out of Quantico, Virginia.

Mag - Short for magazine, which is the ammunition feeding device on just about all weapons apart from revolvers (cylinder) and belt-fed firearms (belt).

OHWS - Offensive Handgun Weapon System. This is the US Military's program to encourage development of a versatile, accurate, and powerful handgun that could be used as a primary CQB weapon. The most notable result is the H&K Mk23 pistol, which was adopted as the standard handgun of US SOCOM.

PDW - Personal Defense Weapon. A military program created to encourage the development of a compact, versatile and accurate firearm for use by aircrews and armor personnel. The first notable result was the H&K MP5K PDW which is similar to a standard MP5K but has a folding stock and a threaded barrel to accept a flash- or sound-suppressor. Several manufacturers have released personal defense weapons, and even H&K has replaced the MP5-based PDW with a newer design.

SAS - Special Air Services. A British elite military unit that routinely undertakes special operations.

SD - SchallDaempfer - German for sound suppressor. The SD designation is used on MP5 series submachine guns with the built-in sound suppressor only.

SEAL - SEa, Air, and Land. This is the acronym that is the name of the US Navy's elite special operations program. There are several SEAL units in operation, each having their own area of specialty (desert warfare, jungle warfare, counter-terrorism, etc.).

Sig - Schweitzerische Industrie Gesellschaft - German for Swiss Industrial Corporation. This company makes fine handguns and rifles on which a number of Airsofts are based.

SOCOM - Special Operation COMmand. This is the military organization that oversees the activities of such elite units as the US Navy SEALs and US Army Delta Force among others.

TM - Abbreviation for Tokyo Marui, a Japanese company that is the predominant manufacturer of spring and electric Airsoft guns.