I'm not sure specifically as it depends on the individual who created it. 'Blue blood' might refer to a noble or elite status, and 'Jamie' could be a character. An 'oc' is often an original character. So it could be a fanfic about a story involving Jamie, an original character in a world related to blue - blood or high - society.
Well, without having read it, 'blue blood jamie oc fanfic' could potentially be a fan - created story. 'Blue blood' usually implies something to do with the upper class or nobility. 'Jamie' is the name of a character, perhaps the main focus. And 'oc' stands for original character. It might be a story that combines elements of high - society drama with the adventures or relationships of Jamie and the original character.
Since I haven't actually read this 'blue blood jamie oc fanfic', it's hard to say exactly. However, 'blue blood' may symbolize a posh or aristocratic setting. 'Jamie' is likely a character in the story. And the 'oc' part indicates an original character created by the fanfic author. It could be a story full of intrigue, romance, or conflict set within a blue - blooded context and centered around Jamie and the original character.