Ronin Jedi.

"A ronin is Kenobi -- a Jedi without an Order."

- Coruscanti Jedi mistress Yaddle, referring to Obi-Wan Kenobi

The ronin Jedi were a loose association of Jedi who lived and operated throughout the Known Galaxy in the long centuries between the Ruusan Reformations and the Great Jedi Purge.

History
Ronin Jedi weren't actually a sect of Jedi but individual Jedi Knights who -- for one reason or another -- did not belong to any greater sect of Jedi. While not unorthodox gray or dark Jedi, ronin Jedi did not strongly adhere to dogmas and traditions, choosing instead to follow their own eclectic paths in the Force. As such, they greatly resembled the pre-Sith War Jedi Knights of old.

Characteristics
The characteristics which defined ronin Jedi were, ironically, their lack of defining characteristics.