Source : Webster's Revised Unabridged Dictionary (1913)

Rerebrace \Rere"brace`\ (r?r"br?s"), n. [F. arri?re-bras.] (Anc.
   Armor)
   Armor for the upper part of the arm. --Fairholt.

Source : WordNet®

rerebrace
     n : cannon that provides plate armor for the upper arm [syn: {upper
         cannon}]