It means original character, atau peminat character. People create them for fantoms and such. I have a Hetalia one, Oregon, along with a bunch of people from our RP.
OC= Original Character I have a few, one of them that will probably never see that fanfiction world (I do not siarkan my Sopranos fics) is Sonia Moltisanti...the lebih level headed twin sister of mafia man Christopher Moltisanti. (TMI I know)