There are many terms used within the airsoft field that one should be familiar with. After all, you do not want to have to keep asking, “Uhh… what does that mean?” Here is a long list of definitions to help anybody get acquainted with airsoft.

AEG: Automatic Electric Gun. The most popular kind of gun on the market.

After-market parts: Anything you can purchase to upgrade or enhance your gun.

BB: Ball bearing. 6mm and spherical, this is the ammunition used in airsoft. The most common weights of BBs are .12g and .20g.

BDU: Battle Dress Uniform. The clothing and gear worn by a player during an airsoft game.
Breech: Where the BB sits immediately before being fired.

CA: Classic Army, a popular manufacturer of airsoft guns.

Chronograph: The device used to test the speed of a projectile, usually to determine if the speed is a safe rate.

CQB: Close quarters battle. Airsoft guns designated as CQB usually have a lower power and are meant to be fired at a close range.

EBB: Electric Blow-Back. These are pistols in which the slide moves backwards and forwards when being fired. While this increases realism, it decreases power, as energy must be diverted to power the blow back effect instead of being focused on the actual firing of the projectile.
FPS: Feet per second, a measure of the velocity of airsoft projectiles.

GBB: Gas Blow-Back. Similar to the EBB, except more realistic and powerful.
Hi-Cap: High capacity magazines. Can hold hundreds of BBs, and usually require a wheel at the bottom of the magazine that needs to be wound occasionally to keep upward feeding pressure on the BBs.

Hop-Up: A device which increases the range of an airsoft gun, by putting backspin on each individual pellet.

Low-cap: Reliable magazines which hold fifty to one hundred BBs.

Mechbox (aka Gearbox): The mechanism which enables AEGs to function.

Mid-Cap: Medium capacity magazines that function as well as low-cap magazines but can hold more BBs.
ROF: The rate of fire. Usually measured in RPM, rounds per minute. If an airsoft gun can shoot 500 rounds in 1 minute, it would have an ROF of 500RPM.
Slide: The primary moving section of an automatic airsoft gun. It takes a round from the magazine, loads it into the breech, and fires it.

Zeroing: The process of making your shots align with the sight of the gun.

Justin Kander, the author, sells airsoft guns on his e-commerce website, http://www.eastcoastairsoft.com.