A list of terms and stuff that might be handy to clear some things up for new players (building on Vector's suggestion). Please add to this by directly editing this post or by posting additions in code, so an admin can copy them from your post.
OP - Opening post
PM - Personal Message
NR - New Republic
MR - Mid Republic
CIS - Confederacy of Independent Systems
IC - In Character (speaking as your role-playing character)
OOC - Out Of Character (speaking as you personally)
RP - Role-play (usually indicates a specific thread)
GM - Game Master (manages a single RP thread, usually the creator)
NPC - Non-Player(playable) Character (a, usually ancillary, character that doesn't belong to a real person)
Nerf Herder - "peasant", "idiot", "moron"
Sithspawn/spit - "Goddamnit"
Godmod(d)ing - The act of autoing or powermoding
Powermoding - Giving your character an unfair advantage like constant regeneration, constant dodging of attacks etc where it is not possible.
Autoing - Deciding for another player, like "Player A shoots Player B who dies". Is generally accepted when used properly, but frowned upon when used to degrade or defeat someone.