[quote=Kaga]
NPC means non-player-character, meaning anyone can play them, so we wouldn't need GS to post first. You're thinking of a GMC, which can only be controlled by the GM.
[/quote]

I've heard of that kind of definition being used for that context, though more times than not, NPC does mean that the GMs control them. I have seen exceptions like mooks, but for the most part, NPCs and GMCs are one in the same.