An Autarkis is a vampire that remains outside the larger vampire society of a given city and often refuses to acknowledge the claim of a Prince, Archbishop, sect, clan or other such entity.
They are absolutely and totally on their own without protection or support from any society.
One may become an Autarkis either voluntarily, by retreating from sect and clan politics entirely, or involuntarily, by being forcibly excommunicated by one's sect. Kindred from and loyal to an Independent clan are known as Independents. There is no such thing as an Independent Brujah, they are Autarkis.
Since most clans are a combination of cultural, political, and hereditary ties, to be labeled Autarkis, thus not belonging to the sect of the clans, may entail being labeled a Caitiff, but that is not necessarily true. Becoming an Autarkis does not change the blood of the Kindred, but mostly severs the social political ties with the clan proper.
The Encyclopaedia Vampyrica defines an Autarkis as "A Kindred refusing to be part of Cainite Society and to recognize a prince's domain." This definition could support the interpretation that the term would be Camarilla exclusive, used to describe non-Camarilla vampires. However, in chapter two of the book Sins of the Blood (devoted to the subjects of Autarkis, Anarchs, and sect-swappers), the term Autarkis is evidently used by both the Camarilla and the Sabbat to define unaligned Kindred.
However, being an Autarkis does not make one an Anarch, as although the Anarchs derive their name from the root word Anarchy, the Anarchs do not share any unifying political ideology, but rather a philosophy of egalitarianism. If there were any position more vulnerable than being a Caitiff, it would be being an Autarkis.