Following the suggestion of one very helpful commenter, I'm gonna go ahead and add the glossary here for all you non-gamer/gun enthusiasts.

GUNS AND GEAR

DMR – Designated Marksman Rifle

Description: ‘DMR’ is the term used to describe (primarily) semi-automatic rifles used by designated marksmen infantry. They are similar to sniper rifles, though usually have more rounds per magazine, and are used for targets that are out of range for most other infantry, excluding snipers.

SVD – Snaiperskaia Vintovka Dragunova

Description: The SVD is a DMR that was developed in the early 1960s by the Soviet Union.

AR-15 – Colt AR-15 (Carbine)

Description: The AR-15 is, typically, a semi-automatic rifle, however, in KillStreak, it has a select-fire modification so as to increase its effectiveness in-game.

AS50 – Accuracy International AS50

Description: The AS50 is a semi-automatic sniper rifle that fires .50 BMG rounds, and was developed in the UK. Its primary use is as an anti-materiel rifle, however, it is often used as a long-range anti-personnel rifle in KillStreak.

.50 BMG – .50 Browning Machine Gun round

Description: The .50 BMG rounds were originally developed for the Browning machine gun in the early 20th century, and have since been utilized in modern weaponry, including, but not limited to, high-caliber sniper rifles.

BTR – Bronetransportyor (BTR-90)

Description: The BTR is an APC designed by the Russians. The version used in KillStreak is the BTR-90, and comes equipped with interchangeable weapons, including, but not limited to, an autocannon, a laser-cannon, and twin-mounted HMGs.

APC – Armored Personnel Carrier

Description: An APC is, typically, a heavily armored vehicle used to transport infantry into and out of battle at speed while protecting them from small arms fire and explosives.

HMG – Heavy Machine Gun

Description: A HMG is a machine gun that uses large rounds being fired at a high rate to destroy vehicles and structures.

Bowie – Bowie Knife

Description: A Bowie is a large fighting knife with a clip point, and typically has a crossguard.

Flash Hider – Flash Suppressor

Description: A Flash Hider is a weapon attachment that masks muzzle flash.

V-22 – Bell Boeing V-22 Osprey

Description: The V-22 is a U.S. military aircraft capable of VTOL while also maintaining speed over long distance travel where an airplane would typically be used.

Other Terms

SDCC – San Diego Comic-Con

RL – Real Life

CS – Computer Science

Scrub – Scrub is a slang term in gaming that refers to someone playing in an unsportsmanlike way, or in a way that is seen as ‘cheap’ or ‘easy’.

Finger-Guns – To shoot someone with finger-guns refers to the act of snapping one’s fingers then pointing one’s index fingers at a subject, object, or situation.

Echolalia – Echolalia refers to the repetition of words or vocalizations, and is typically symptomatic of someone with a disorder such as Autism or Asperger’s Syndrome, and can include the adoption of accents or vocal tics.

ASAFP – As Soon As Fucking Possible

Muzzle Flash – Muzzle Flash refers to the bright light visible at the end of a firearm’s barrel when it’s discharged.

VTOL – Vertical Take-Off and Landing