Let's compile some tf2 terminology and such that newer players might not be familiar with when you scream it at them over VC.
Most of the basic stuff is covered at the official wiki:
http://wiki.teamfortress.com/wiki/Glossary_of_player_termsBut we have a lot of terms that aren't covered there as well, or deserve special mention here just because they are used so much

.
Post suggestions here:http://www.tf2newbs.com/forum/index.php/topic,6750.0.html A AirshotTo shoot someone in the air. Usually refers to Grenades or Rockets.
B C D Demoknight Demoman using one of the various sword+shield loadouts
DRDead Ringer, a spy cloak watch that fakes death
E Engineer/Engie NestA spot where an engineer has set up their sentry, dispenser and sometimes teleporter
F Fatty, fatboyHeavy Weapons Guy
HWG, Heavy
Facestab Wonky hit boxes, or excuses for a backstab registering when a spy stabs you from the front
G H HWG, HeavyHeavy Weapons Guy
I IntelThe 'intelligence' (briefcase); also used to refer to the basement/room in which it is located.
J K L M Med Medic
N NS - Nice Shot O OP Overpowered
P Popped/popA medic used their ubercharge
Q R S Scoot Scout
SG, SentryThe Engineers sentry gun.
Solly Soldier
SpyroSpy disguised as Pyro
T Turtling When an engineer stays between their dispenser and sentry and just hits their sentry with their wrench.
U V Vanilla Using stock weapons [the default]
W W+M1 A pyro that holds down Left Mouse and walks forward. Typically an overexaggeration
WTBWilling to buy/Want to buy
X Y Z