an acronym for "
Out of Character".
Frequently used in one of two situations:
1. in
role-playing, indicating that a person is making a comment, suggestion, etc., that isn't coming from the character but from the person him- or herself.
2. in fanfiction,
signaling that the way the author chose to portray the characters (or perhaps unintentionally portrayed them) may not be consistent with how the characters act, think, or speak in the original work on which the fanfiction is based.
OOC is most often used as an adjective, but can also be used as an adverb or, in less common cases, a verb.