Terminology

Action
the part of the gun that loads and discharges the projectile.
Back Spin
a BBs' rearward rotation resulting from contact with the Hop-Up nub.
Barrel
the hollow metal tube through which the projectile passes and exits. The breech is located at the rearmost end of the barrel and the muzzle is at the front.
BBs
the plastic 6mm or 8mm ammunition used in Airsoft guns. BB-guns use .177 metal BB ammunition.
Blowback
a portion of the energy used in semi or full automatic pistols and rifles is used to cause the slide or bolt to move backwards to provide a more realistic firing cycle and feel. Blowback features can be powered by gas or electric Airsoft power-plants. GBB (Gas Blowback), NBB (Non-Blowback) and EBB (Electronic Blowback) are abbreviations you'll encounter under this category. Many places offer pistol only combat activities for gamers.
CQB
Close Quarter Battle (roughly 10 to 70 feet fast action combat).
Dead Man Walking
a player who has been hit and announces that he's out of the game and walks off the field or exits the combat area.
Duty Weapon
standard weapons issued to military, special ops or law enforcement personnel.
Effective Range
the range at which the combination of the gun's capability and shooter's ability can deliver accurate shot placement.
Field Gaming
battles that take place in open fields or forest area and require skilled team play to approach the enemy within target range. Field gaming sites limit Airsoft guns to 400fps and up to 500fps for sniper rifles.
Flash Hider
the tip of the Airsoft gun that is designed to look like the flash containment device found at the muzzle of many military issue assault rifles. In the United States, the Airsoft flash hiders must include at least .25" of permanent blazed orange.
FPE
foot pounds of energy. A system used to calculate the power of a projectile at the muzzle or at a given distance. FPE is not a significant measure of an Airsoft gun's appropriateness for gaming. Airsoft guns produce very low FPE.
FPS
feet per second. FPS is a very important measure used in determining how effective and appropriate an Airsoft gun is for particular types of gaming. Gaming ranges have a limit on maximum FPS allowable. Most CQB game ranges only permit Airsoft guns that shoot under 350 FPS.
Full Auto
squeezing and holding the trigger will result in constant firing of successive rounds until the ammo is exhausted or the shooter releases the trigger.
Gear Up
putting on eye and face protection and other game clothing/gear in preparation for an Airsoft battle/skirmish.
Green Gas
Propellant used in gas powered Airsoft guns. Green Gas in made up of polysiloxane lubricant (silicone) and propane.
HFC-143a
Propellant used in gas powered Airsoft guns. This gas was used in air-conditioners and refrigerators.
Honor System
an ethical conduct standard used by Airsoft gamers requiring that a hit player voluntarily acknowledges when he is hit and removes himself from active play for the remainder of the skirmish/battle.
Hop Up System
an adjustable mechanical system that is used to cause BBs passing through the Hop-Up to spin rearwards/backwards. The backspin extends the range of the BBs flight allowing the shooter to engage targets at extended distances.
Laser
a target acquisition device that is mounted on the accessory rail and projects a red or green laser light that is adjusted (sighted in) to match a certain point of aim at a given distance.
Magazine
a removable or fixed compartment that holds a capacity of ammunition to be fed into the firing mechanism.
Mainspring
the coiled spring that is compressed to power the internal piston in a Springer or AEG Airsoft gun.
Mechbox
This is the heart of an AEG. The Mechbox component, using electrically powered spurred gears, compresses and releases the mainspring that powers the piston, which results in creating the compression chamber psi needed to send the BB down the barrel and towards the target.
Own
a term used to refer to enemy targets (gamers) that you shot (took out of play) during battle. Example: I "owned" three enemy troops during the skirmish.
Pain Penalty
the level of "ouch factor" that you feel when hit by an opponent's ammo. The closer the range the higher the pain penalty.
POA
Point Of Aim.
POI
Point Of Impact.
Rechargeable Battery
the reusable power source supplied with AEG Airsoft.
RIS
Rail Interface System or sometimes referred to as Rail Installation System. It's an accessory mounting rail.
Rise
a BB that passes though a Hop-Up System has a trajectory that rises above the bore path when the wind resistance meets the back-spinning BB. See Hop-Up.
ROF
Rate Of Fire refers to the number of BBs that can be discharged within a given span of time (second/minute).
RPM
Rounds Per Minute.
RPS
Round Per Second.
Scope
an optical sight used in acquiring a target at extended ranges.
Semi Auto
a shot is discharged with each squeeze of the trigger. The firing cycle re-cocks the gun and feeds the next round into firing position awaiting the next trigger squeeze.
Skirmish
a fight or military conflict between squads/troops detached from base-camps of opposing armies.
Smooth Bore
the bore in Airsoft guns do not have rifling groves cut into the inner walls of the barrel. The BBs are perfectly round and would not benefit from the spiral effects of rifling. Rifling will deform the plastic BBs. The smooth bore walls allow the BBs to retain a backspin when imparted by the Hop-Up system.
SOC
State Of Charge refers to the remaining battery current/amperage.
Speed Loader
a device that makes loading BBs more efficient.
Spin-up
see back-spin.
Trajectory
the path of a projectile in fight.
Upgradeability
The ability of an Airsoft gun to be modified to improve mechanical performance, as well as adding accessories to outfit (e.g. adding a laser sight, flashlight, optics, etc.) the gun for particular team-play scenarios.