Out of character (
OOC) is usually concerned with
role playing or fan fictions. It's when one person
1. either stops writing/typing as that character and speaks as them self to whoever is reading.
2. The character that is being used isn't acting like that character will act. Often happens because someone doesn't know that much about the fandom or just not very experienced with that character.
Often someone will try to warn that they will be
Out Of Character at some points or in all.