The Collaborative International Dictionary of English v.0.48:

Rerefief \Rere"fief`\ (r?r"f?f`), n. [F. arri[`e]re-fief. See
   Rear hinder, and Fief.] (Scots Law)
   A fief held of a superior feudatory; a fief held by an under
   tenant. --Blackstone.
   [1913 Webster]