Tank jargon

Coax: A machine gun mounted co-axially that moves with the main gun.
KE: An armour-piercing round utilizing kinetic energy to penetrate armour.
HEAT: High-explosive anti-tank, a round that uses chemical energy to penetrate armour.
HE-Frag: Tank round that works like a massive hand grenade. used against infantry.
HESH: High-explosive squash head, a HE round that defeats armour by sending a shockwave through the steel, breaking off large pieces of armour material inside.
ATGM: Anti-tank guided missile. a long-range missile that is guided towards it's target, by an operator.
RPG: Rocket-propelled grenade.
SPAAG: Self-propelled anti-air gun.

Spall: Fragments of steel that is generated by a round penetrating armour.
GPS: Gunners primary sight.
TIS: Thermal imaging sight.
TTS: Tank thermal sight (on M60A3).
TOGS: Thermal sight on challenger.
IFV: Infantry Fighting Vehicle, a vehicle capable of supporting it's dismounts with heavy firepower.
APC: Armoured Personnel Carrier. An armoured battle taxi.
Tank: Heavily armoured vehicle, with no infantry.
Tank-destroyer: Lightly armoured vehicle with a large gun/ATGM.
TOW: Tube-launched, Optically-tracked, Wire command data link, ATGM.

Fully Exposed: No part of the vehicle hidden.
Hull down: Hull is hidden behind a berm.
Turret down: Hull and turret is hidden behind a berm, with only commander looking over it.
Fully Concealed: No part of the vehicle (or crew) visible.